Synchronization of wireless transmitted MRI signals in MRI system

• US 7,123,009 B1
• Filed: 09/22/2005
• Issued: 10/17/2006
• Est. Priority Date: 09/22/2005
• Status: Active Grant

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Inventors: Scott, Greig C.
• Primary Examiner(s): Gutierrez, Diego
• Assistant Examiner(s): Vaughn, Megann E
• Application Number:
  US11/233,669
• Time in Patent Office: 390 Days
• Field of Search: 324/311, 324/322
• US Class Current: 324/311
• 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

Abstract

In a MRI system having a FID detector unit and a computer unit for processing FID signals, phase errors introduced into the FID signal at the detector unit are corrected at the computer unit by transmitting a pilot signal from the computer unit to the detector unit, processing the pilot unit along with a detected FID signal at the detector unit, transmitting the processed signals to the computer unit, obtaining the pilot signal and FID signal at the computer unit, and combining the pilot signal and the FID signal whereby phase errors cancel.

Claims

1. In a MRI system having a FID detector unit and a computer unit for processing FID signals, a method of correcting for phase errors introduced when processing a FID signal at the detector unit and transferring the processed FID signal from the detector unit comprising:

a) providing a pilot signal at the detector unit,

b) detecting the pilot signal and the FID signal at the detector unit,

c) modulating a carrier signal with the pilot signal along with the detected FID signal at the detector unit for transmission to the processing unit as a single side band of the modulated carrier signal,

d) receiving and frequency down converting the modulated carrier signal at the computer unit to recover the pilot signal and the FID signal, and

e) combining the recovered pilot signal and the recovered FID signal whereby phase error is cancelled.

2. The method of claim 1 wherein the pilot signal is generated in the detector.

3. The method of claim 1 wherein the pilot signal is transmitted from the computer unit to the detector.

4. The method of claim 1 wherein step d) includes mixing the recovered pilot signal and the recovered FID signal to obtain a difference frequency Δ

f.

5. The method of claim 4 wherein the frequency of the pilot signal is near the frequency of the FID signal.

6. The method of claim 4 wherein frequency of the pilot signal (Fp) is at the difference frequency, Δ

f, from the frequency of the FID signal (Fp+Δ

f).

7. The method of claim 6 wherein the difference frequency signal (Δ

f) is mixed with a signal at the frequency of the FID signal offset by the difference frequency thereby obtaining an output signal at the frequency of the FID signal.

8. The method of claim 7 wherein the signal at the frequency of the FID signal offset by the difference frequency is less than the frequency of the FID signal.

9. In a MRI system having a FID detector unit and a computer unit for processing FID signals, a method of correcting for phase errors introduced in the FID signal at the detector unit comprising the steps of:

a) providing a pilot signal at the detector unit,

b) processing with a carrier signal the pilot signal along with a detected FID signal at the detector unit for transmission to the computer unit, and

c) recovering the pilot signal and FID signal at the computer unit,

d) using phase of the pilot signal transmitted by the detector unit as an error signal in correcting for phase error introduced into the FID signal at the detector unit.

10. The method of claim 9 wherein the pilot signal is generated in the detector.

11. The method of claim 9 wherein the pilot signal is transmitted from the computer unit to the detector.

12. The method of claim 9 wherein step c) includes use of a transponder for modulating and transmitting the pilot signal and the FID signal to the computer unit.

13. The method of claim 12 wherein step d) includes obtaining a difference between the pilot signal and the FID signal.

14. The method of claim 13 wherein the recovered FID signal and the recovered pilot signal transmitted by the detector unit are each frequency down converted.

15. The method of claim 14 wherein step c) includes mixing the recovered pilot signal and the recovered FID signal to obtain a difference frequency signal.

16. The method of claim 15 wherein frequency of the pilot signal is at a difference frequency, Δ

f, from the frequency of the FID signal.

17. The method of claim 16 wherein the difference frequency signal is mixed with a signal at the frequency of the FID signal offset by the difference frequency thereby obtaining an output signal at the frequency of the FID signal.

18. The method of claim 17 wherein the signal at the frequency of the FID signal offset by the difference frequency is less than the frequency of the FID signal.

19. The method of claim 9 wherein step b) uses analog to digital signal conversion.