Frequency swept excitation for magnetic resonance

• US 7,403,006 B2
• Filed: 10/11/2006
• Issued: 07/22/2008
• Est. Priority Date: 10/11/2005
• Status: Active Grant

• Current Assignee: Regents of The University of Minnesota (University of Minnesota)
• Original Assignee: Regents of The University of Minnesota (University of Minnesota)
• Inventors: Idiyatullin, Djaudat S., Garwood, Michael
• Primary Examiner(s): Shrivastav; Brij B.
• Assistant Examiner(s): Vargas; Dixomara
• Application Number:
  US11/548,664
• Publication Number:
  US 20070188171A1
• Time in Patent Office: 650 Days
• Field of Search: 324300-322, 600410-435
• US Class Current: 324/310
• CPC Class Codes: G01N 24/081 Making measurements of geologic samples, e.g. measurements of moisture, pH, porosity, permeability, tortuosity or viscosity
• 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
• CPC Class Codes: G01R 33/4816 NMR imaging of samples with ultrashort relaxation times such as solid samples, e.g. MRI using ultrashort TE [UTE], single point imaging, constant time imaging
• CPC Class Codes: G01R 33/54 Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console

Abstract

A method of magnetic resonance is provided that uses a frequency swept excitation wherein the acquired signal is a time domain signal is provided. In one embodiment, the sweeping frequency excitation has a duration and is configured to sequentially excite isochromats having different resonant frequencies. Acquisition of the time domain signal is done during the duration of the sweeping frequency excitation. The time domain signal is based on evolution of the isochromats.

Claims

1. A method comprising:

applying a sweeping frequency excitation having a duration, the sweeping frequency excitation being configured to sequentially excite isochromats having different resonant frequencies;

acquiring a time domain signal during the duration, the time domain signal being based on evolution of the isochromats; and

using the acquired time domain signal to create a magnetic resonance image.

2. The method of claim 1, further comprising applying a static magnetic field during applying the sweeping radio frequency excitation.

3. The method of claim 1, wherein acquiring a time domain signal continues after the duration.

4. The method of claim 1, wherein acquiring a time domain signal begins before the duration.

5. The method of claim 1, wherein applying the sweeping frequency excitation comprises applying a sweeping frequency excitation using a transmitter and wherein acquiring the time domain signal comprises detecting the signal on a receiver.

6. The method of claim 5, wherein the transmitter and receiver are decoupled.

7. The method of claim 1, further comprising generating a first spectra based on a correlation of a Fourier transform of the applied sweeping frequency excitation and a Fourier transform of the acquired time domain signal.

8. The method of claim 7, further comprising generating a second spectra based on a processing of the acquired time domain signal in a frequency domain and averaging the first and second spectra.

9. The method of claim 1, further comprising generating spectra based on deconvoluting the applied sweeping frequency excitation and the acquired time domain signal to generate a deconvoluted signal and Fourier transforming the deconvoluted signal.

10. The method of claim 9, further comprising generating a second spectra based on a processing of the acquired time domain signal in a frequency domain and averaging the first and second spectra.

11. The method of claim 1, further comprising applying a field gradient to create an image.

12. The method of claim 1, wherein applying the sweeping frequency excitation comprises applying a phase modulation.

13. The method of claim 1, wherein applying the sweeping frequency excitation comprises applying a frequency modulation.

14. The method of claim 1, wherein the time domain signal is based on evolution of magnetization of the isochromats.

15. The method of claim 1, further comprising processing the acquired time domain signal before using the acquired time domain signal to create a magnetic resonance image.

16. A method comprising:

applying a sweeping frequency excitation having a duration, the sweeping frequency excitation being configured to sequentially excite isochromats having different resonant frequencies, wherein applying the sweeping frequency excitation includes applying a plurality of discrete excitation pulses;

acquiring a time domain signal during the duration, the time domain signal being based on evolution of the isochromats, wherein acquiring the time domain signal includes sampling between excitation pulses; and

using the acquired time domain signal to create a magnetic resonance image.