Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
  • A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
  • G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
  • G01R33/34—Constructional details, e.g. resonators, specially adapted to MR
  • G01R33/34046—Volume type coils, e.g. bird-cage coils; Quadrature bird-cage coils; Circularly polarised coils
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
  • G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
  • G01R33/36—Electrical details, e.g. matching or coupling of the coil to the receiver
  • G01R33/3628—Tuning/matching of the transmit/receive coil

Definitions

• the present subject matter pertains generally to medical imaging and more specifically to surface and volume coils for magnetic resonance imaging and spectroscopy procedures.
• a radio frequency magnetic field unit or coil
• the object to be imaged is placed within the magnetic field unit.
• the magnetic field unit is driven by an excitation signal that stimulates a nuclear induction (free induction decay) signal in the object, which, in turn, is received by a radio frequency coil.
• the nuclear induction signal includes information characteristic of the object being imaged.
• the information in the induction signal can be used to identify chemicals and to diagnose diseases.
• radio frequency magnetic field units are used to image different portions of a patient depending on such variables as, for example, the patient size and shape and the biomedical region of interest.
• the magnetic field unit selected is typically a compromise between performance, size, cost and availability. Consequently, the images resulting from the use of a particular radio frequency magnetic field unit may be inadequate for their intended purpose.
• Fig. 1 includes a schematic of a magnetic resonance system according to one embodiment of the present subject matter.
• Fig. 2A includes a perspective view of a volume coil according to one embodiment of the present subject matter.
• Fig. 2B includes a section view along cut line 2B-2B of Fig. 2A.
• Fig. 2C includes a view of connections for electrically connecting a current element of the volume coil to circuitry according o one embodiment.
• Fig. 3 A includes a view of a volume coil according to one embodiment of the present subj ect matter.
• Fig. 3B includes a section view along cut line 3B-3B of Fig. 3 A.
• Fig. 3C includes a view of a current element according to one embodiment of the present subject matter.
• Fig.4 includes a view of a current element according to one embodiment of the present subject matter.
• Fig. 5 includes a flow chart of a method according to one embodiment of the present subject matter.
• Fig. 6 includes a flow chart of a method according to one embodiment of the present subject matter.
• Fig. 1 includes a schematic of system 100 according to one embodiment.
• magnet 10 provides a static magnetic field for magnetic resonance imaging.
• coil 20A Disposed within the magnetic field is coil 20A.
• Coil 20A provides a radio frequency field for both exciting the region of interest and for detecting signals from the region of interest.
• Coil 20A is connected to switch 25 and control 55.
• control 55 includes an impedance control.
• Switch 25, sometimes referred to as a transmit-receive switch is connected to receiver 40 and transmitter 50, each of which are connected to system console 60.
• Console 60 is also connected to switch 25 by line 45. Console 60 applies a signal to line 45 to select between a receive mode and a transmit mode for coil 20A.
• console 60 When in transmit mode, as determined by a control signal on line 45, console 60 supplies a radio frequency signal to transmitter 50 and the output of transmitter 50 is delivered to coil 20A.
• Transmitter 50 provides a radio frequency excitation signal to coil 20A.
• Console 60 in one embodiment, modulates a signal, or radio frequency current, delivered to coil 20A.
• transmitter 50 provides an excitation signal having a modulated amplitude, frequency or phase. The specimen is subjected to a static magnetic field concurrent with both the transmit and receive mode.
• Console 60 in one embodiment, includes a processor or controller.
• Receiver 40 in one embodiment, includes a signal detector.
• Transmitter 50 in one embodiment, includes a power amplifier.
• coil 20A includes a dedicated receiver coil connected to one or more receiver channels.
• coil 20A includes a dedicated transmitter coil connected to one or more transmitter channels.
• two or more coils 20 A are used with at least one coil dedicated for transmitting and at least one coil dedicated for receiving.
• transmitter 50 includes a single transmitter having multiple output channels, each of which is selectively operable.
• transmitter 50 provides a quadrature signal to coil 20A via multiple independent channels.
• transmitter 50 of the figure represents multiple transmitters, each connected to a separate current element of coil 20A.
• console 60 transitions to a receive mode.
• console 60 When in receive mode, console 60 provides a signal on line 45 to instruct switch 25 to connect coil 20 A with an input of receiver 40.
• Receiver 40 supplies an electrical signal to console 60 based on the received signal generated by coil 20A.
• Coil 20A generates an electrical signal based on a received signal which is generated by the specimen.
• receiver 40 includes multiple receive channels, each of which is selectively operable. For example, in one embodiment, receiver 40 receives multiple signals from coil 20 A via multiple independent channels. In one embodiment, receiver 40 of the figure represents multiple receivers, each connected to a separate current element of coil 20A.
• the current flowing in coil 20A is modulated by console 60, transmitter 50 or switch 25.
• the radio frequency current flowing in coil 20A in one embodiment, is circularly polarized. Circular polarization entails sequentially driving individual segments of the coil in a manner that creates a circularly polarized field within the coil. Circular polarization is also referred to as quadrature drive. In various embodiments, the phase, frequency or amplitude of the radio frequency current is modulated.
• Control 55 is connected to coil 20A and console 60.
• Console 60 supplies a signal to control 55 to select a value of a parameter of a particular current element or group of current elements. In one embodiment, the parameter includes impedance.
• a program executing on console 60 determines the impedance of one or more current elements of coil 20A.
• the impedance of a current element is adjusted by changing a dielectric constant between conductors of the current element, by changing an inductance, by changing capacitance or by changing a resistance.
• control 55 provides a direct current control signal to an adjustable component of coil 20A.
• at least one phase shifter is connected to at least one current element of the coil.
• a phase shifter allows control of the phase of a signal propagating on the coil.
• Phase shifters include delay lines, PIN diodes or reactive components that allow selective control of a phase.
• the coil of the present subject matter is tuned to a particular resonant frequency by adjusting a PIN diode or other devices. In one embodiment, the coil of the present subject matter is detuned from a particular resonant frequency by adjusting a PIN diode or other devices.
• the coil of the present subject matter is tuned to multiple resonant frequencies.
• Console 60 is connected to memory 75, user input 80, printer 65 and display 70.
• Memory 75 provides storage for data and programming accessible to console 60.
• Memory 75 includes random access memory, read only memory, removable storage media, optical media, magnetic media or other digital or analog data storage.
• User input 80 includes a user accessible input device, including, for example, a keyboard, a mouse or other pointing device, an optical device, touch sensitive screen or microphone.
• Printer 65 includes hardware for producing a printed output, or paper copy, and in various embodiments, includes a laser printer, dot matrix printer or an ink jet printer.
• Display 70 includes hardware for generating a visible image based on data from console 60, and in one embodiment, includes a liquid crystal display, cathode ray tube display or other computer monitor. Other functions and features may be present in a magnetic resonance imaging console.
• Fig. 2A includes a perspective view of coil 20B according to one embodiment of the present subject matter.
• Coil 20B includes eight current elements arranged in the shape of a cylindrical wall. Each current element includes a pair of linear conductors separated by a dielectric. The dielectric, in one embodiment, is disposed along at least a portion of the length of the linear conductors. The conductors arranged substantially in parallel with each other and substantially in parallel with a central axis of the volume enclosed by the cylindrical wall. Dielectric 110 is disposed between an inner conductor 120A and an outer conductor 115 A.
• each current element includes an inner conductor 120 A and an outer conductor 115 A, each in the form of a conductive strip, and inlaid on dielectric 110.
• a view of current element 130A is illustrated in section view Fig. 2B.
• inner conductor 120 A and outer conductor 115A of a current element are mounted on a surface of dielectric 110.
• inner conductor 120 A is aligned with outer conductor 115 A.
• inner conductor 120 A includes a conductor having a circular cross section as, for example, a wire, rod or tube.
• both inner conductor 120A and outer conductor 115A are foil strips.
• outer conductor 115A includes a screen, mesh or perforated conductive material.
• Inner conductor 120 A and outer conductor 115 A are fabricated of copper. Other .conductive materials are also contemplated, including, for example, aluminum or semiconductor materials.
• inner conductor 120 A and outer conductor 115A include thin conductive plating applied by semiconductor fabrication methods, including for example, electroplating, vapor deposition, or etching or by adhesive bonding.
• Each current element 130 A of coil 20B is sufficiently spaced apart from an adjacent current element to be electrically reactively decoupled. In one embodiment, each current element 130A is sufficiently close that adjacent current elements are reactively coupled.
• Dielectric 110 in one embodiment, includes polytetrafluoroethylene (PTFE) or Teflon® or other non-conductive material. In the embodiment illustrated, dielectric 110 is a continuous section of tubular material, however, discrete segments may also be held in alignment to create a volume coil. In one embodiment, the dielectric includes air, liquid or other fluid.
• PTFE polytetrafluoroethylene
• Teflon® Teflon®
• Coil 20B of Fig. 2A is suited for use as a volume coil, such as, for example, a head coil or body coil. Coil 20B of Fig. 2A can be used as a transmit coil, a receive coil or both and in one embodiment, the coil is used for parallel imaging.
• Fig. 2C illustrates one embodiment of electrical contacts or connections for connecting current element 130A of coil 20 A with the structure and circuitry of Fig. 1.
• outer conductor 115A is connected to terminal 117 by link 116 and inner conductor 120 A is connected to terminal 122 by link 121.
• Terminals 117 and 122 in one embodiment, each include a binding post or other threaded fastener.
• Links 116 and 121 each include a segment of electrical wire.
• the wire is soldered to a lug affixed to a terminal and either an inner conductor or outer conductor.
• links 116 and 121 include conductive traces on an insulator.
• Other contacts or electrical connections are also contemplated, such as, for example, a cable electrically connected to the coil and fitted with an electrical connector.
• an electrical connection includes a soldered connection.
• a component such as a capacitor, PIN diode or both
• Radio frequency signal and direct current (DC) control leads are also soldered across the gap between inner conductor 120 A and outer conductor 115 A.
• the radio frequency leads are attached to a TR switch, preamplifier, power amplifier or some combination thereof.
• the DC leads in one embodiment, are attached to a PIN diode driver or voltage bias source.
• the connection point in one embodiment, is positioned across a gap disposed anywhere on the current element.
• Fig. 3A illustrates coil 20C according to the present subject matter.
• coil 20C includes twenty current elements 130B arranged about a volume. More or less than twenty current elements are contemplated for other embodiments.
• Each current element 130B is sufficiently close to an adjacent element 13 OB to be reactively coupled.
• Each current element 13 OB includes an outer conductor 115B and in inner conductor 120B arranged in parallel alignment, with each aligned on axis 160 through the center of the volume.
• Dielectric 110B is disposed between each current element 130B.
• each current element 130B includes outer conductor 115B.
• the segments are electrically connected together at connector 140.
• Connector 140 in one embodiment, also provides an electrical connection to coil 20C.
• Other electrical connections to coil 20C are provided at connector 130B at one end and at connector 150 at a second end.
• a discontinuity is provided at a point along the length of the current element, such as, for example, gap 165 disposed near the midpoint.
• Gap 165 in various embodiment, provides improved current distribution for the current element or improved shielding of contact points for the inside sample volume.
• An electrical connection in various embodiments, includes a binding post, a soldered joint, or other electrical connector.
• the outer conductor is split into more than two segments.
• some current elements have multiple segment outer conductors and other current elements have a single segment outer conductor.
• at least one inner conductor 120B is segmented or split. At the gaps between segments or splits, a contact point may be provided for connecting components. Examples of components include capacitors, inductors, PIN diodes, voractors, radio frequency cable attachment points, DC control lines or other components.
• Fig. 3B includes a section view along cut line 3B-3B of the embodiment in Fig. 3 A.
• outer conductors 115B are set atop a surface of dielectric HOB and inner conductors 120B are set below a surface of dielectric HOB.
• the figure illustrates a segmented dielectric with two segments shown as well as two portions of segments. Adjacent dielectric segments, in one embodiment, are joined together by an adhesive, mechanical fastener or by other fastening means. Adjacent dielectric segments, in one embodiment, are continuous. Adjacent outer conductor segments 115B are separated by a space, or slot.
• Fig. 3C illustrates current element 130B according to one embodiment, such as that shown in Figs. 3 A and 3B.
• the figure illustrates two segments, or sections, of outer conductor 115B separated by gap 165.
• Each segment of outer conductors 115B is connected by electrical component 155.
• component 155 includes a reactive component, such as, for example, an electrical capacitor.
• component 155 includes an electrical wire, an inductor, a resistor, or other combination of passive or active electrical components.
• electrical component 155 is adjustable such that an electrical parameter or quality can be selectively varied.
• Electrical component 155 is connected to outer conductor 115B at connectors 140.
• Connector 140 in one embodiment, includes a solder point.
• current element 130B includes connection points disposed on either side of a gap in the current element between outer conductor 115B and inner conductor 120B. In one embodiment, current element 130B includes connection points disposed at a strategically selected point on the current element. In one embodiment, current element 130B includes connectors 145 disposed at ends of outer conductor 115B. A portion of inner conductor 120B is illustrated and includes a connector 150. In one embodiment, one or more radio frequency signals are provided to coil 20B or received from coil 20B. In one embodiment, one or more control signals are provided to coil 20B or received from coil 20B. The radio frequency signals or control signals are electrically connected to coil 20B across gaps positioned at 140, 145 or 150 or at other positions selected on a current element.
• Electrical component 155 includes a PIN diode, a transistor, a voractor, a phase shifter or other active electrical component.
• Electrical component 155 in various embodiments, includes a capacitor, an inductor, a filter, a TR switch, a preamplifier circuit or a power amplifier feed point.
• electrical component 155 includes circuitry to adjust the electrical coupling between the segments of outer conductor 115.
• electrical component 155 includes a voltage biasing circuit to adjust a PIN diode connected between the segments.
• electrical component 155 includes a circuit to adjust modulation of a transistor connected between the segments.
• component 155 includes a voractor or silicon controlled rectifier.
• Fig. 4 illustrates current element 130C according to one embodiment of the present subject matter.
• current element 130C includes outer conductor 115C and inner conductor 120C separated by an air dielectric.
• outer conductor 115C includes a thin copper foil connected to insulator copper foil end plates 170.
• Inner conductor 120C includes a metallic rod or shaft or copper foil strip.
• the present subject matter can be used for active shimming of radio frequency fields or for selecting a slice plane or volume in a specimen under observation.
• the present subject matter can be operated under control of console 60 or operated manually or operated by other controlling circuitry. The following describes methods of using the present subject matter.
• Fig. 5 illustrates a flow chart of method 500 according to one embodiment of the present subject matter.
• the method starts at 505 and proceeds to 510 where the coil is positioned about a patient or other nuclear magnetic resonance active sample.
• the coil is placed to generate a field at the region of interest.
• this entails positioning coil 20A within magnet 10, as illustrated in Fig. 1, and placing a body or specimen within the volume.
• a body coil according to the present subject matter is built into a bore of a magnet.
• a radio frequency field is generated within the volume.
• the driving signal for the radio frequency field is provided by transmitter 50 of Fig. 1 and connected to coil 20A by switch 25 in response to a signal on line 45 from console 60.
• the transmitter signal in one embodiment, is divided in a power splitter to feed multiple current elements.
• the image uniformity or other desired parameter within the volume, or at the region of interest is measured.
• the parameter includes a particular measure of field homogeneity.
• the parameter is selected to optimize imaging at the region of interest.
• an inquiry is presented to determine if the measured parameter is satisfactory. If not satisfactory, then the procedure continues at 530 wherein the coil is adjusted. Coil adjustment can be performed, for example, by changing an inductance value, a capacitance value or a resistance value or other the value of other components or circuit functions for one or more current elements of the coil.
• an impedance adjustment will result in a change of amplitude, phase or frequency of the current flowing in the coil.
• processing continues at 515 where the radio frequency field is again generated. If the field or other measurement criteria are met following the inquiry at 525, then the method ends at 540.
• the measurement criteria may entail determining if the field is sufficiently homogenous. The foregoing procedure is a description of negative feedback.
• the radio frequency field generated by the coil is manipulated to remove the artifact and improve the heart image uniformity.
• the independently controllable current elements are adjusted to compensate for radio frequency field inhomogeneities created by radio frequency wave propagation and loss phenomena in the anatomy.
• the radio frequency field (sometimes referred to as the Bi field) is produced by the coil at the Larmour frequency.
• Radio frequency shimming in the manner described herein, is used to adjust, manipulate, or steer the radio frequency field to approximately optimize the field for a nuclear magnetic resonance measurement at a region of interest.
• the present subject matter is used to produce a desired radio frequency field gradient.
• the radio frequency field gradient allows for selective excitation of the imaging volume, as illustrated, for example, by method 600 of Fig. 6.
• the procedure begins at 605 and proceeds to 610 where the coil is positioned at a region of interest.
• the region of interest may include a portion of a human body or other specimen to be imaged.
• a slice or volume is selected for signal acquisition.
• the slice in one embodiment, includes a three dimensional volume in the region of interest.
• an impedance or other property of one or more current elements is adjusted to select a particular slice or volume in the object.
• the data is acquired for the selected slice or volume.
• the method ends at 630.
• the amplitude and phase of the field gradient can be changed during an imaging scan by a variety of signal acquisition protocols. Gradient selection, in the manner described herein, can be used to improve the Bi field over each slice or volume element in a multiple slice scan.
• the impedance of a current element is adjusted by changing an impedance.
• the impedance can be changed, for example, by adjusting a dielectric in the core of an inductor or by changing the spacing of windings or by other means of changing the inductance.
• the capacitance of a current element is adjusted by changing a capacitor.
• the impedance can be changed by adjusting a dielectric between plates of the capacitor or by changing the spacing on the plates or by other means of changing the capacitance.
• the impedance is changed by physically adjusting a core or dielectric element.
• control of the procedures shown in Fig. 5 and Fig. 6 are executed by a console, a processor or other circuitry adapted to execute a procedure.
• console 60 in Fig. 1 includes a processor executing programming to adjust an impedance or select a region of interest for imaging.
• the impedance of each current element of the present subject matter is independently adjustable. For example, in one embodiment, the impedance of a first current element can be increased while that of a second current element can be reduced without regard for the impedance of the first current element. In one embodiment, the impedance of multiple current elements in a group are adjusted as a unit.
• a threaded shaft is rotated to move a core within an inductor for a number of current elements, thereby changing the dielectric constant and thus, the impedance.
• Individual current elements can be adjusted independently to achieve a particular value or parameter and yet, as a whole a group of current elements can be adjusted to achieve a particular strategy.
• the radio frequency field within the volume of a coil is dependent, in part, on the electrical properties of the anatomy or other sample to be imaged. For example, in a magnetic field of 7 T, the wavelength in air is approximately one meter (m) whereas the wavelength in human brain tissue is approximately 12 centimeters (cm). Thus, upon introduction of a human head into the volume of the coil, the radio frequency magnetic field within the head load is distorted by the electrical properties of the head. These anatomy, or load dependent distortions will often result in a non- uniform image. To create a more homogenous, or uniform image in such a coil, the impedance of one or more current elements can be independently adjusted to compensate for load dependent Bi field distortions.
• the present subject matter is adapted for use with imaging systems, such as, for example, spectroscopy systems, magnetic resonance imaging systems, nuclear magnetic resonance imaging systems, functional magnetic resonance imaging systems, and electron spin resonance systems.
• imaging systems such as, for example, spectroscopy systems, magnetic resonance imaging systems, nuclear magnetic resonance imaging systems, functional magnetic resonance imaging systems, and electron spin resonance systems.
• the present subject matter is adapted for used with a technology utilizing a radio frequency coil.
• the present subject matter includes a solenoidal coil, a planar (surface) coil, a half-volume coil, a volume coil, a quadrature coil or a phased array coil, each of which include one or more current elements as described herein.
• a surface coil in one embodiment, includes a plurality of parallel current elements in adjacent alignment.
• a first radio frequency coil is used to transmit an excitation signal and a second radio frequency coil is used to receive a signal from the object or specimen under investigation.
• the present subject matter is adapted for parallel imaging.
• a plurality of one or more independent current elements are used to receive a signal.
• the signals received by each current element are combined through post processing to form a composite image.
• a processor or console receives the plurality of signals and compiles the image.
• an excitation signal is provided by one or more current elements and each current element is reactively decoupled from an adjacent current element.
• the present subject matter includes programming to cause an imaging system to perform shimming or gradient selection.
• the programming is adapted to run on a processor or console connected to a radio frequency coil.
• the programming may include instructions for operation by the processor or console.
• the impedance or other coil control component are manually adjustable.
• the present subject matter includes a computer-accessible or machine-accessible storage medium with instructions and data to execute a method described herein.
• the present subject matter includes a plurality of current elements as described herein.
• the current elements include wave guides, cavities, transmission line segments, microstrip segments or coaxial line segments.
• the present subject matter is used for interactive image optimization or negative feedback optimization.
• one current element is electromagnetically decoupled from an adjacent current element. While, in some embodiments, a measurable amount of coupling may exist between adjacent current elements, nevertheless, it is understood that adjacent current elements are adequately decoupled for certain purposes, such as, for example, performing parallel imaging.
• Decoupling in one embodiment, includes physically separating adjacent current elements by a distance sufficient to reduce electromagnetic coupling. By introducing adequate physical separation, the field from one current element will have a de minimis effect on the field of an adjacent current element.
• Electronic circuitry can also be used to decouple current elements. For example, in one embodiment, a suitably sized capacitor or inductor provides substantial decoupling of adjacent current elements.
• each current element may be described as a discrete resonant current element in that elements do not rely on current flowing in an end-ring for proper operation.
• the current path in a current element is substantially confined to the inner and outer conductors and current significant to the operation of the coil does not flow in an end-ring structure.
• an end ring is provided.
• a parameter associated with a radio frequency field is measured to gauge performance of the coil. Parameters may be measured in- situ or in conjunction with the development of a magnetic resonance image or nuclear magnetic resonance spectra.
• the parameter is determined interactively in an iterative process of measuring and adjusting an adjustable component of a current element of the coil.
• the parameter includes field homogeneity.
• the parameter includes signal intensity.
• the signal amplitude of images or spectra is used as parameter.
• the parameter includes determining how much power is needed to achieve a predetermined intensity in a region.
• the parameter includes signal to noise ratio.
• Other parameters include the field of view, relaxation constants (such as TI and T2), echo time (TE) and repetition time (TR).
• a phase shifter is used to adjust the current phase in individual current elements.
• a phase shifter in various embodiments, includes a delay element, capacitor or a PIN diode circuit.
• radio frequency transmit signal amplitude is controlled by the power amplifier gain.
• Receiver signal amplitude in one embodiment, is controlled by the gain of a preamplifier.
• the frequency of a radio frequency signal is controlled by an inductor or capacitor.
• capacitance can be provided by a discrete capacitor or distributed capacitance.
• inductance can be provided by a discrete inductor or distributed inductance.
• a component of a current element is adjusted to establish a desired radio frequency field within the coil.
• the field can be manipulated to provide a suitable bias to compensate for body-caused artifacts.
• the bias is maintained.
• the bias is switched to progress across a region of interest over a period of time. By sweeping the bias across the region of interest, individual slices or volumes can be selected at different times.
• the current elements are electromagnetically decoupled. Transmitting using such a coil, in one embodiment, includes driving each current element directly from a single transmitter signal divided and distributed to the elements by means of a power splitter rather than relying on inductive coupling for signal propagation. In one embodiment, multiple power amplifiers are dedicated to respective current elements in the coil.
• the present subject matter includes a plurality of discrete resonant current elements each disposed about a region of interest.
• Each current element includes pair of parallel conductors that are separated by a dielectric.
• Each current element includes an adjustable component.
• the adjustable component includes a capacitance, an inductance, a voractor, a PIN diode, or a phase shifter.
• a preamplifier (or receiver) is connected to a current element.
• a transmitter is connected to a current element.
• a radio frequency filter circuit is connected to a current element.
• a transmit-receive switch is connected to the first current element.
• a combiner is connected to two or more current elements.
• a power splitter is connected to two or more current elements.
• a component control line connected to the first current element and is adapted to control the adjustable component.
• the component control line in various embodiments, includes a direct current or alternating current control signal.
• a pair of current elements are electromagnetically decoupled.
• a system in one embodiment, includes a radio frequency coil and a console connected to an adjustable component of a current element of the coil.
• the console is adapted to control the adjustable component.
• the current element is connected to the console by a transmitter. In one embodiment, the current element is connected to the console by a receiver. In one embodiment, the current element is connected to the console by a control line that is connected to the adjustable component. In one embodiment, the console includes programming to provide radio frequency field shimming. In one embodiment, the console includes programming to select a radio frequency field gradient. In one embodiment, the console includes programming to provide parallel signal excitation. In one embodiment, the console includes programming to provide parallel signal reception. Parallel signal excitation and reception are used with parallel imaging.
• a method includes positioning a sample relative to a radio frequency coil. In one embodiment, this entails placing the sample adjacent the coil. In one embodiment, this entails placing the sample within a volume of the coil.
• the method includes comparing a parameter with a predetermined value.
• the measured parameter includes a radio frequency field dependant parameter associated with nuclear magnetic resonance . If the measured nuclear magnetic resonance parameter is unsatisfactory, then the method entails adjusting the adjustable component to achieve a satisfactory nuclear magnetic resonance value.
• the method includes adjusting an impedance, a capacitance, an inductance, a PPM diode or adjusting a phase.
• the method includes adjusting a preamplifier connected to a current element.
• the method includes adjusting a transmitter connected to a current element.
• the method includes adjusting a radio frequency filter circuit, a transmit-receive switch, or a component control line connected to a current element.
• a method according to the present subject matter includes positioning a sample relative to a radio frequency coil having a first current element and a second current element. The method includes adjusting adjustable components of the first current element the second current element to achieve a satisfactory nuclear magnetic resonance value and processing a signals received from the two current elements using a parallel imaging routine.
• the method includes an article having a machine-accessible storage medium including stored data, wherein the data, when accessed, results in a machine performing a method.
• the method includes determining a parameter of a field in a region of interest proximate a radio frequency coil and adjusting an impedance of a first current element at a time when an impedance of a second current element remains fixed.
• the impedances are adjusted such that the impedances cause the parameter to be satisfied.
• the parameter includes determining image uniformity.
• the second impedance is adjusted without affecting the first impedance.
• a reactive component is adjusted.

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• 2003
  • 2003-04-21 KR KR10-2004-7016826A patent/KR20040103981A/ko not_active Application Discontinuation
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  • 2003-04-21 EP EP03747048A patent/EP1497668A1/de not_active Withdrawn
  • 2003-04-21 AU AU2003262371A patent/AU2003262371A1/en not_active Abandoned
  • 2003-04-21 WO PCT/US2003/012393 patent/WO2003089947A1/en active Application Filing
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