SIMULTANEOUS TX-RX FOR MRI SYSTEMS AND OTHER ANTENNA DEVICES

• US 20120223709A1
• Filed: 02/28/2012
• Published: 09/06/2012
• Est. Priority Date: 02/28/2011
• Status: Active Grant

• Current Assignee: Life Services, LLC
• Original Assignee: Life Services, LLC
• Inventors: Schillak, Scott M., Vaughan, John Thomas Jr., Lemaire, Charles A., Waks, Matthew T.
• Granted Patent: US 9,097,769 B2
• Time in Patent Office: Days
• US Class Current: 324/309
• CPC Class Codes: G01R 33/3415 comprising arrays of sub-coils , i.e. phased-array coils with flexible receiver channels
• CPC Class Codes: G01R 33/3607 RF waveform generators, e.g. frequency generators, amplitude-, frequency- or phase modulators or shifters, pulse programmers, digital to analog converters for the RF signal, means for filtering or attenuating of the RF signal
• CPC Class Codes: G01R 33/3614 RF power amplifiers
• CPC Class Codes: G01R 33/3621 NMR receivers or demodulators, e.g. preamplifiers, means for frequency modulation of the MR signal using a digital down converter, means for analog to digital conversion [ADC] or for filtering or processing of the MR signal such as bandpass filtering, resampling, decimation or interpolation
• CPC Class Codes: G01R 33/3692 involving signal transmission without using electrically conductive connections, e.g. wireless communication or optical communication of the MR signal or an auxiliary signal other than the MR signal
• CPC Class Codes: G01R 33/54 Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console

Abstract

Apparatus and method that are more efficient and flexible, and obtain and connect high-power RF transmit signals (TX) to RF-coil devices in an MR machine or other devices and simultaneously receive signals (RX) and separate net receive signals NRX) of interest by subtracting or filtering to remove the subtractable portion of the transmit signal (STX) from the RX and preamplifying the NRX and signal processing the preamplified NRX. In some embodiments, signal processing further removes artifacts of the transmitted signal, e.g., by digitizing the NRX signal, storing the digitized NRX signal in a memory, and performing digital signal processing. In some embodiments, the present invention also includes pre-distorting the TX signals in order to be better able to identify and/or remove the remaining artifacts of the transmitted signal from the NRX signal. This solution also applies to other high-power RF-transmit-antennae signals.

Claims

1. A method comprising:

providing a magnetic-resonance (MR) coil having a plurality of antenna elements;

locating the MR coil in a bore of an MR magnet;

transmitting an MR transmit signal (TX signal) using the MR coil;

receiving an MR receive signal (RX signal) using the MR coil simultaneously with the transmitting of the MR transmit signal (TX signal);

removing artifacts of the TX signal from the received MR receive signal (RX signal) to form a net received signal (NRX signal); and

processing the net received signal (NRX signal) and generating MR output data from the processed NRX signal.

2. The method of claim 1, wherein the removing artifacts of the transmit signal from the received MR receive signal further includes:

splitting an RF pulse into a first portion and a second portion, wherein the first portion is amplified and transmitted as the MR transmit signal (TX); and

subtracting the second portion from the received MR receive signal (RX) to form the NRX signal.

3. The method of claim 1, wherein the transmitting of the MR transmit signal (TX) includes:

transmitting a first high-power RF pulse; and

coupling the first high-power RF pulse to at least the first antenna element but not to the second antenna element and coupling the second high-power RF pulse to at least the second antenna element but not to the first antenna element, wherein the power amplifying is performed in the bore of the MR magnet.

4. The method of claim 1, further comprising coupling heat from the power amplifying the first RF pulse primarily to the first antenna element, and coupling heat from the power amplifying the second RF pulse primarily to the second antenna element.

5. The method of claim 1, wherein the first RF pulse has a power of less than one watt and the first high-power pulse has a power of at least 100 watts.

6. The method of claim 1, wherein the first RF pulse has a power of less than one watt and the first high-power pulse has a power of at least 1000 watts.

7. The method of claim 1, further comprising electrically controlling an impedance of the first antenna element to match an impedance of the power amplifying.

8. The method of claim 1, further comprising using a programmable information-processing device operatively coupled to control operation of the power amplifying in the MRI coil from a location at least one meter away from the MRI coil.

9. The method of claim 1, further comprising:

using a programmable information-processing device operatively coupled to control operation of the power amplifying in the MRI coil from a location at least one meter away from the MRI coil;

electrically controlling an impedance of the first antenna element to match an impedance of the power amplifying; and

using a feedback signal operatively coupled to the programmable information-processing device to provide feedback control in order to control the impedance of the first antenna element.

10. The method of claim 1,

wherein the transmitting of the TX signal further includes:

generating a radio-frequency (RF) pulse-sequence (PS) signal having a plurality of RF pulses each characterized by an RF carrier frequency;

filtering the RF PS signal to remove a plurality of RF frequency components from the RF PS signal while substantially not removing a frequency component of the RF PS signal having a frequency equal to the RF carrier frequency, and outputting a resulting filtered pulse-sequence signal; and

power amplifying the filtered pulse-sequence signal to form the TX signal; and

wherein the removing artifacts of the TX signal from the received RX signal further includes;

filtering the RX signal to remove at least the plurality of RF frequency components that were not removed from the RF PS signal, and outputting a resulting filtered RX signal as the NRX signal.

11. The method of claim 1,

wherein the transmitting of the TX signal further includes:

generating a radio-frequency (RF) pulse-sequence (PS) signal having a plurality of RF pulses each characterized by an RF carrier frequency;

comb filtering the RF PS signal to remove alternating ones of a plurality of RF frequency components from the RF PS signal while substantially not removing a frequency component of the RF PS signal having a frequency equal to the RF carrier frequency, and outputting a resulting filtered pulse-sequence signal; and

power amplifying the filtered pulse-sequence signal to form the TX signal; and

wherein the removing artifacts of the TX signal from the received RX signal further includes;

comb filtering the RX signal to remove at least the alternating ones of the plurality of RF frequency components that were not removed from the RF PS signal, and outputting a resulting filtered RX signal as the NRX signal.

12. The method of claim 1,

wherein the transmitting of the TX signal further includes:

generating a radio-frequency (RF) pulse-sequence (PS) signal having a plurality of RF pulses each characterized by an RF carrier frequency;

surface-acoustic-wave (SAW) filtering the RF PS signal to remove selected ones of a plurality of RF frequency components from the RF PS signal while substantially not removing a frequency component of the RF PS signal having a frequency equal to the RF carrier frequency, and outputting a resulting filtered pulse-sequence signal;

power amplifying the filtered pulse-sequence signal to form the TX signal; and

wherein the removing artifacts of the TX signal from the received RX signal further includes;

SAW filtering the RX signal to remove at least the selected ones of the plurality of RF frequency components that were not removed from the RF PS signal, and outputting a resulting filtered RX signal as the NRX signal.

13. The method of claim 1,

wherein the transmitting of the TX signal further includes:

generating a radio-frequency (RF) pulse-sequence (PS) signal having a plurality of RF pulses each characterized by an RF carrier frequency;

preprocessing the RF PS signal to form a preprocessed transmit signal;

distributively power amplifying the preprocessed transmit signal within the bore of the the MR magnet to obtain a high-power RF signal; and

coupling the high-power RF signal to the plurality of antenna elements in the bore of the MR magnet;

wherein the removing artifacts of the TX signal from the received RX signal to form the NRX signal further includes preamplifying to form the NRX signal after the removing of the artifacts of the TX signal;

the method further comprising;

controlling the distributively power amplifying and the preamplifying of the received RF signals by frequency and impedance matching signals.

14. A non-transient computer-readable medium having instructions stored thereon for causing a suitably programmed information processor to execute a method in a magnetic-resonance (MR) system that includes a coil having a plurality of antenna elements located a bore of an MR magnet, the method comprising:

transmitting an MR transmit signal (TX signal) using the MR coil;

receiving an MR receive signal (RX signal) using the MR coil simultaneously with the transmitting of the MR transmit signal (TX signal);

removing artifacts of the TX signal from the received MR receive signal (RX signal) to form a net received signal (NRX signal); and

processing the net received signal (NRX signal) and generating MR output data from the processed NRX signal.

15. An apparatus comprising:

an MR magnet that has a bore;

a magnetic-resonance (MR) coil that has a plurality of antenna elements located in the bore of the MR magnet;

a transmitter operably coupled to, and configured to transmit an MR transmit signal (TX signal) from, the MR coil;

a receiver configured to receive an MR receive signal (RX signal) from the MR coil simultaneously with the transmission of the MR transmit signal (TX signal);

an artifact remover circuit configured to remove artifacts of the TX signal from the received MR receive signal (RX signal) to form a net received signal (NRX signal); and

a processor configured to process the net received signal (NRX signal) and to generate MR output data from the processed NRX signal.

16. The apparatus of claim 15, wherein the artifact remover further includes:

a splitter configured to split an RF pulse into a first portion and a second portion, wherein the first portion is amplified and transmitted as the MR transmit signal (TX); and

a subtractor circuit configured to subtract the second portion from the received MR receive signal (RX) to form the NRX signal.

17. The apparatus of claim 15, wherein the transmitter includes a plurality of power amplifiers, including a first power amplifier and a second power amplifier both located in the bore of the MR magnet, and wherein the first power amplifier is further configured to couple a first high-power RF pulse to at least the first antenna element but not to the second antenna element and the second power amplifier is configured to couple a second high-power RF pulse to at least the second antenna element but not to the first antenna element.

18. The apparatus of claim 17, further comprising a first heat-transmission coupler configured to couple heat from the first power amplifier primarily to the first antenna element, and a second heat-transmission coupler configured to couple heat from the second power amplifier primarily to the second antenna element.

19. The apparatus of claim 17, wherein the first power amplifier receives a signal that has a power of less than one watt and generates the first high-power pulse to have a power of at least 100 watts.

20. The apparatus of claim 17, wherein the first power amplifier receives a signal that has a power of less than one watt and generates the first high-power pulse to have a power of at least 1000 watts.