Method and remotely adjustable reactive and resistive electrical elements
Apparatus and method that includes providing a variable-parameter electrical component in a high-field environment and based on an electrical signal, automatically moving a movable portion of the electrical component in relation to another portion of the electrical component to vary at least one of its parameters. In some embodiments, the moving uses a mechanical movement device (e.g., a linear positioner, rotary motor, or pump). In some embodiments of the method, the electrical component has a variable inductance, capacitance, and/or resistance. Some embodiments include using a computer that controls the moving of the movable portion of the electrical component in order to vary an electrical parameter of the electrical component. Some embodiments include using a feedback signal to provide feedback control in order to adjust and/or maintain the electrical parameter. Some embodiments include a non-magnetic positioner connected to an electrical component configured to have its RLC parameters varied by the positioner.
1. A method comprising:
providing an RF circuit in a remote environment, wherein the RF circuit includes an electrical component having a characteristic impedance at a resonance frequency of the RF circuit in the remote environment;
changing a characteristic of the remote environment that affects the characteristic impedance and the resonance frequency of the RF circuit;
sensing a parameter of the RF circuit and generating an electrical feedback signal based on the sensed parameter; and
based on the electrical feedback signal, automatically changing the electrical component to adjust both the characteristic impedance and the resonance frequency.
2. The method of claim 1 , wherein the automatically changing includes moving part of the electrical component using a non-magnetic mechanical-movement device that comprises moving using a piezo-electric motor.
3. The method of claim 2 , wherein the electrical component comprises an inductor, and wherein at least one of its parameters includes an inductance.
4. The method of claim 2 , wherein the electrical component comprises an antenna, and wherein at least one of its parameters includes a length.
5. The method of claim 1 , wherein the electrical component comprises a capacitor, and wherein at least one of its parameters includes a capacitance.
6. The method of claim 1 , wherein the electrical component includes a first antenna element having a movable portion that moves relative to another portion, the first antenna element having an adjustable resonant frequency, the method further including: based on an electrical signal, automatically moving the movable portion of the first antenna element in order to vary the resonance frequency.
7. The method of claim 1 , wherein the electrical component includes a first antenna element having an adjustable physical length, and wherein the method further includes automatically changing the physical length of the first antenna element.
8. The method of claim 1 , further comprising using a programmable information-processing device operatively coupled to control an automatically moving of a movable portion of the electrical component.
9. The method of claim 8 , wherein the electrical component comprises a first antenna element having an electrical length, and wherein the automatically moving includes using a non-magnetic mechanical-movement device to adjust the electrical length of the first antenna element.
10. A computer-readable medium having instructions stored thereon for causing a suitably programmed information processor to execute a method that comprises:
sensing a parameter of an RF circuit in a remote environment, wherein the RF circuit includes an electrical component having a characteristic impedance at a resonance frequency of the RF circuit in the remote environment, and wherein a characteristic of the remote environment is changed that affects the characteristic impedance and the resonance frequency of the RF circuit; generating an electrical feedback signal based on the sensed parameter; and
based on the electrical feedback signal, automatically changing the electrical component to adjust both the characteristic impedance and the resonance frequency.
11. The computer-readable medium of claim 10 , wherein the automatically changing includes moving part of the electrical component using a piezo-electric motor.
12. The computer-readable medium of claim 11 , wherein the electrical component comprises an inductor, and wherein at least one of its parameters changed by the piezo-electric motor includes an inductance.
13. The computer-readable medium of claim 11 , wherein the electrical component comprises a antenna element, and wherein at least one of its parameters changed by the piezo-electric motor includes a length of the antenna.
14. The computer-readable medium of claim 10 , wherein the electrical component comprises a capacitor, and wherein at least one of its parameters that is adjustable includes a capacitance.
15. The computer-readable medium of claim 10 , wherein the electrical component includes a first antenna element having a movable portion that moves relative to another portion, the first antenna element having an adjustable resonant frequency, the computer-readable medium further comprising instructions such that, based on an electrical signal, the automatically moving moves the movable portion of the first antenna element in order to vary the adjustable resonant frequency.
16. The computer-readable medium of claim 10 , wherein the electrical component includes a first antenna element having an adjustable physical length, and wherein the computer-readable medium further includes instructions such that the automatically moving changes the physical length of the first antenna element.
17. The computer-readable medium of claim 10 , wherein the electrical component includes a plurality of antenna elements having a resonant frequency, and wherein the computer-readable medium further includes instructions such that the automatically moving results in adjusting the resonant frequency and the characteristic impedance of the plurality of antenna elements at the resonant frequency.
18. The computer-readable medium of claim 10 , wherein the electrical component comprises a first antenna element having an electrical length, and wherein the automatically moving, using a non-magnetic mechanical-movement device includes adjusting the electrical length of the first antenna element.
19. An apparatus comprising:
an RF circuit in a remote environment, wherein the RF circuit includes an electrical component having a characteristic impedance at a resonance frequency of the RF circuit in the remote environment, and wherein when a characteristic of the remote environment is changed the change affects the characteristic impedance and the resonance frequency of the RF circuit;
a sensor that senses a parameter of the RF circuit and generates an electrical feedback signal based on the sensed parameter; and
an information-processing control system that, based on the electrical feedback signal, automatically changes the electrical component to adjust both the characteristic impedance and the resonance frequency.
20. The apparatus of claim 19 , wherein the remote environment is inside a magnetic-resonance imager, and wherein the characteristic of the remote environment that is changed is a position of a patient in the magnetic-resonance imager.
21. The method of claim 1 , wherein the automatically changing includes moving part of the electrical component using a piezo-electric motor.
22. The method of claim 1 , wherein the automatically changing includes using a programmable information-processing device to control automatically moving of a movable portion of the electrical component.
23. The method of claim 1 , wherein the electrical component is part of an RF coil in a magnetic-resonance imaging system.
24. The method of claim 1 , wherein the automatically changing includes automatically changing the electrical component to match a desired impedance and a desired resonant frequency.
25. The method of claim 24 , wherein the desired impedance and the desired resonant frequency is the characteristic impedance and the resonance frequency of the RF circuit prior to the changing of the characteristic of the remote environment that affects the characteristic impedance and the resonance frequency of the RF circuit.
26. The method of claim 25 , wherein the electrical component is part of an RF coil and the remote environment includes a magnetic-resonance imaging system and further comprising determine the desired impedance and the desired resonant frequency before an imaging subject is placed in the magnetic-resonance imaging system to cause the changing of the characteristic of the remote environment.
27. The computer-readable medium of claim 11 , wherein the electrical component is part of an RF coil in a magnetic-resonance imaging system.