Magnetic resonance non-balanced-SSFP method for the detection and imaging of susceptibility related magnetic field distortions

• US 7,567,081 B2
• Filed: 05/03/2007
• Issued: 07/28/2009
• Est. Priority Date: 05/03/2007
• Status: Active Grant

• Current Assignee: University of Basel
• Original Assignee: University of Basel
• Inventors: Scheffler, Klaus, Bieri, Oliver
• Primary Examiner(s): Shrivastav; Brij B.
• Assistant Examiner(s): Fetzner; Tiffany A
• Application Number:
  US11/743,712
• Publication Number:
  US 20080272774A1
• Time in Patent Office: 817 Days
• Field of Search: 324300-322, 600407-435
• US Class Current: 324/309
• CPC Class Codes: G01R 33/286 involving passive visualization of interventional instruments, i.e. making the instrument visible as part of the normal MR process
• CPC Class Codes: G01R 33/5613 Generating steady state signals, e.g. low flip angle sequences [FLASH]
• CPC Class Codes: G01R 33/5614 using a fully balanced steady-state free precession [bSSFP] pulse sequence, e.g. trueFISP

Abstract

Disclosed are methods and apparatuses for generating susceptibility-related contrast images, as induced, e.g., by marker material interventional devices used for passive MR-guided interventions, or by particles or cells loaded with marker materials used for molecular imaging, cell-tracking or cell-labeling. Near a local magnetic field perturber a positive contrast signal emanates from local gradient compensation to form, e.g., a balanced SSFP type of echo, whereas everywhere else echoes are shifted outside of the data acquisition window.

Claims

1. A method of magnetic resonance imaging (MRI) within a MRI apparatus comprising:

providing a non-balanced (nb) steady state free precession (SSFP) protocol in which spins are in steady-state while the imaging gradient itself is non-balanced wherein spins are dephased so that signal(s) are suppressed in an MRI image,

subjecting material having magnetic susceptibility to said non-balanced SSFP protocol wherein said material causes a local magnetic field distortion generating local field gradients,

wherein said local field gradients generated from said material compensate for said dephased spins of the nb-SSFP locally so that said dephased spins of the nb-SSFP are rephrased in order to provide a local signal from the material having magnetic susceptibility which is utilized in generating an MRI image from the MRI apparatus.

2. The method of claim 1, wherein said signal is a hyperintense positive signal.

3. The method of claim 1, wherein said protocol is a non-balanced SSFP sequence, wherein the rephased spins result locally in a balanced SSFP.

4. The method of claim 1, wherein the spins within one TR are dephased by 2π

about 2π

or a multiple thereof.

5. The method of claim 4, wherein the spins within one TR are dephased by 4π

or about 4π

.

6. The method of claim 1, wherein said dephasing occurs along the readout gradient (Gx), the phase encode gradient (Gy), the slice selection gradient (Gz) or a combination thereof.

7. The method of claim 1, wherein said local field gradients fully compensate for said dephased spins.

8. The method of claim 3, wherein said local field gradients fully compensate for said dephased spins.

9. The method of claim 1, wherein said material having magnetic susceptibility is a diamagnetic, paramagnetic or a ferromagnetic material.

10. The method of claim 9, wherein said material is a ferromagnetic material.

11. The method of claim 1, wherein said MRI image is one dimensional, two dimensional or three dimensional.

12. The method of claim 1, wherein said material having magnetic susceptibility is in a confined area and wherein said non-balanced SSFP protocol is a transient non-balanced SSFP phase.

13. The method of claim 12, wherein a signal is detected after said material has been subjected to one to ten excitation pulses of said transient non-balanced SSFP phase.

14. The method of claim 13, wherein said signal is created within 1 to 30 milliseconds, preferably within 1 to 20 milliseconds.

15. The method of claim 14, wherein the material is part of a moving local magnetic field perturber and wherein a projection image of said moving local magnetic field perturber is created by the MRI apparatus.