Low power broadband spin decoupling

• US 7,948,235 B2
• Filed: 03/16/2007
• Issued: 05/24/2011
• Est. Priority Date: 04/11/2006
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Foxall, David L.
• Primary Examiner(s): Arana; Louis M
• Application Number:
  US12/295,942
• Publication Number:
  US 20090096449A1
• Time in Patent Office: 1,530 Days
• Field of Search: 324/307, 324/309
• US Class Current: 324/307
• CPC Class Codes: G01R 33/4616 using specific RF pulses or specific modulation schemes, e.g. stochastic excitation, adiabatic RF pulses, composite pulses, binomial pulses, Shinnar-le-Roux pulses, spectrally selective pulses not being used for spatial selection

Abstract

In a magnetic resonance data acquisition method, magnetic resonance is excited (72, 74) in an observed nuclear species. Magnetic resonance data of the observed nuclear species are acquired (76). A plurality of different broadband decoupling radio frequency pulses (80) configured to decouple a coupled nuclear species from the observed nuclear species are applied. Each broadband decoupling radio frequency pulse has a different or randomized or pseudorandomized amplitude (110) as a function of time. Each broadband decoupling radio frequency pulse has about the same peak power, pulse duration, and frequency spread. The differences between the broadband decoupling radio frequency pulses are effective to substantially suppress cycling sidebands.

Claims

1. A magnetic resonance data acquisition method comprising:

exciting magnetic resonance in an observed nuclear species;

acquiring magnetic resonance data of the observed nuclear species; and

applying a plurality of different broadband decoupling radio frequency pulses configured to decouple a coupled nuclear species from the observed nuclear species, wherein each broadband decoupling radio frequency pulse has a randomized or pseudorandomized amplitude as a function of time, the differences between the different broadband decoupling radio frequency pulses being effective to substantially suppress cycling sidebands.

2. The magnetic resonance data acquisition method as set forth in claim 1, wherein the randomized or pseudorandomized amplitude as a function of time of each broadband decoupling radio frequency pulse has a bilateral reflection symmetry.

3. The magnetic resonance data acquisition method as set forth in claim 1, wherein the randomized or pseudorandomized amplitude as a function of time of each broadband decoupling radio frequency pulse includes a Gaussian white noise or uniformly distributed noise component.

4. The magnetic resonance data acquisition method as set forth in claim 1, wherein the randomized or pseudorandomized amplitude as a function of time of each broadband decoupling radio frequency pulse has principal frequency components at acoustical frequencies.

5. The magnetic resonance data acquisition method as set forth in claim 1, wherein the applying of a plurality of different broadband decoupling radio frequency pulses includes:

applying at least four different pre-recorded broadband decoupling radio frequency pulses; and

repeating the applying to effectuate decoupling of the coupled nuclear species from the observed nuclear species at least over a duration of the acquiring.

6. The magnetic resonance data acquisition method as set forth in claim 1, wherein the applying includes:

obtaining a random or pseudorandom signal as a function of time;

computing a phase as a function of time such that the obtained random or pseudorandom signal and computed phase define one of the broadband decoupling radio frequency pulses; and

repeating the obtaining and computing to define the plurality of different broadband decoupling radio frequency pulses.

7. The magnetic resonance data acquisition method as set forth in claim 6, wherein the applying further includes:

reflecting the obtained random or pseudorandom signal to produce a reflection-symmetric random or pseudorandom signal; and

scaling the obtained random or pseudorandom signal with respect to at least one of time and amplitude such that the defined broadband decoupling radio frequency pulses have about the same peak power and duration.

8. The magnetic resonance data acquisition method as set forth in claim 6, wherein the obtaining of the random or pseudorandom signal as a function of time includes one of:

recording noise as a function of time;

generating the random or pseudorandom signal as a function of time by repeated application of a random or pseudorandom number generator; and

computing a signal having statistical characteristics as a function of time at that at least approximate statistical characteristics of a random or pseudorandom signal as a function of time.

9. A magnetic resonance apparatus for performing the magnetic resonance data acquisition method as set forth in claim 1.

10. A magnetic resonance apparatus comprising:

a main magnet for generating a main magnetic field;

a magnetic resonance excitation system configured to excite magnetic resonance in an observed nuclear species;

a magnetic resonance data acquisition system configured to acquire magnetic resonance data of the observed nuclear species; and

a decoupling system configured to successively apply different broadband decoupling radio frequency pulses configured to decouple a coupled nuclear species from the observed nuclear species, the differences between the different broadband decoupling radio frequency pulses being effective to substantially suppress cycling sidebands, wherein each broadband decoupling radio frequency pulse has randomized or pseudorandomized amplitude as a function of time.

11. The magnetic resonance apparatus as set forth in claim 10, wherein the decoupling system includes:

a random or pseudorandom signal generator;

a broadband decoupling pulse generator that generates the different broadband decoupling radio frequency pulses from random or pseudorandom signals supplied by the random or pseudorandom signal generator; and

a radio frequency transmitter for selectively transmitting the different generated broadband decoupling radio frequency pulses.

12. The magnetic resonance apparatus as set forth in claim 10, wherein the decoupling system includes:

a storage medium storing a broadband pulses library containing the plurality of different broadband decoupling radio frequency pulses having randomized or pseudorandomized amplitude as a function of time; and

a radio frequency transmitter for transmitting different broadband decoupling radio frequency pulses selected from the broadband pulses database.

13. The magnetic resonance apparatus as set forth in claim 10, wherein the different broadband decoupling radio frequency pulses having randomized or pseudorandomized amplitude as a function of time each have about the same peak power, pulse duration, and frequency spread.

14. A decoupling system for decoupling a coupled nuclear species from an observed nuclear species, the decoupling system comprising:

a source providing different broadband decoupling radio frequency pulses each having about the same peak power, pulse duration, and frequency spread, differences between the provided broadband decoupling radio frequency pulses being effective to substantially suppress cycling sidebands; and

a radio frequency transmitter for transmitting the provided broadband decoupling radio frequency pulses.

15. The decoupling system as set forth in claim 14, wherein the source includes:

a storage medium storing a library of pre-recorded broadband decoupling radio frequency pulses each having about the same peak power, pulse duration, and frequency spread, and further having differences effective to substantially suppress cycling sidebands.

16. The decoupling system as set forth in claim 15, wherein the decoupling system is configured to (i) transmit the pre-recorded broadband decoupling radio frequency pulses, and (ii) repeat the transmit of at least some of the pre-recorded broadband decoupling radio frequency pulses conditional upon the transmitting exhausting the stored supply of pre-recorded broadband decoupling radio frequency pulses.

17. The decoupling system as set forth in claim 14, wherein the source includes:

a broadband decoupling pulse generator that generates different broadband decoupling radio frequency pulses from different portions of noise supplied by a random or pseudorandom signal generator.

18. A magnetic resonance apparatus comprising:

a main magnet for generating a main magnetic field;

a magnetic resonance excitation system configured to excite magnetic resonance in an observed nuclear species;

a decoupling system as set forth in claim 14.

19. The decoupling system as set forth in claim 14, wherein the source provides different bilaterally symmetric broadband decoupling radio frequency pulses each having bilateral reflection symmetry and about the same peak power, pulse duration, and frequency spread.