Quantitative single image-based magnetization transfer weighted imaging using an inter-subject normalization reference within the image

• US 7,676,075 B2
• Filed: 08/17/2005
• Issued: 03/09/2010
• Est. Priority Date: 08/17/2004
• Status: Active Grant

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Smith, Seth, Golay, Xavier, van Zijl, Peter C. M.
• Primary Examiner(s): Johns; Andrew W
• Application Number:
  US11/660,361
• Publication Number:
  US 20080199061A1
• Time in Patent Office: 1,665 Days
• Field of Search: 382/128, 382/131, 324/307, 324/309, 600/410
• US Class Current: 382/131
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/407 Evaluating the spinal cord A61B5/4896 takes precedence
• CPC Class Codes: G01R 33/54 Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
• CPC Class Codes: G01R 33/5605 by transferring coherence or polarization from a spin species to another, e.g. creating magnetization transfer contrast [MTC], polarization transfer using nuclear Overhauser enhancement [NOE]
• CPC Class Codes: G01R 33/56509 due to motion, displacement or flow, e.g. gradient moment nulling G01R33/567 takes precedence
• CPC Class Codes: G01R 33/5659 caused by a distortion of the RF magnetic field, e.g. spatial inhomogeneities of the RF magnetic field G01R33/56509, G01R33/56518, G01R33/56536 take precedence
• CPC Class Codes: G06T 2207/10088 Magnetic resonance imaging [MRI]
• CPC Class Codes: G06T 2207/20104 Interactive definition of region of interest [ROI]
• CPC Class Codes: G06T 2207/30004 Biomedical image processing
• CPC Class Codes: G06T 7/0014 using an image reference approach

Abstract

Disclosed is a system and method for generating quantitative imagery of demyelination in the spinal cord. The method includes acquiring a magnetization transfer weighted (MTw) MR image of the spinal column, identifying a reference region of interest within the image corresponding to cerebrospinal fluid (CSF), averaging the signal intensity corresponding to the reference region of interest, and computing a ratio, on a voxel-by-voxel basis, of the signal intensity of each voxel by the averaged reference signal intensity. In doing so, normalized MTw images are obtained such that detrimental artifacts such as motion-induced errors, coil loading, and RF coil sensitivity variations are obviated.

Claims

1. A method for quantifying loss of macromolecular components in tissue, comprising:

acquiring an MTw image of the tissue, the MTw image having a plurality of voxels, wherein each voxel has a corresponding MR signal;

identifying a reference region of voxels within the plurality of voxels, wherein the region of voxels corresponds to a reference material having a minimal magnetization transfer effect;

computing a reference MR signal corresponding to the region of voxels; and

computing a normalized MT weighted image, based on the ratio of the MTw image and the reference MR signal.

2. The method of claim 1, wherein computing the reference MR signal comprises computing an average of a plurality of MR signals corresponding to the region of voxels.

3. The method of claim 1, wherein acquiring the MTw image comprises employing an image acquisition scheme with an MT preparation pre-pulse.

4. The method of claim 1, wherein acquiring the MTw image comprises employing a T2* weighted pulse sequence with an MT pre-pulse.

5. The method of claim 1, wherein the tissue comprises spinal cord tissue.

6. The method of claim 5, wherein the reference material comprises cerebrospinal fluid.

7. The method of claim 1, wherein computing the normalized MT weighted image comprises dividing each MTw signal by the reference MR signal.

8. The method of claim 1, further comprising:

acquiring a second MR image; and

comparing the second MR image with the MT weighted image.

9. An MRI system, comprising:

a main magnet;

a gradient coil;

an RF coil; and

a computer having a computer readable medium encoded with a program for acquiring an MTw image of the tissue, the MTw image having a plurality of voxels, wherein each voxel has a corresponding MR signal;

identifying a reference region of voxels within the plurality of voxels, wherein the region of voxels corresponds to a reference material having a minimal magnetization transfer effect;

computing a reference MR signal corresponding to the region of voxels; and

computing an MTCSF image, based on the MR image and the reference MR signal.

10. The MRI system of claim 9, wherein the program for computing the reference MR signal comprises a program for computing an average of a plurality of MR signals corresponding to the reference region of voxels.

11. The MRI system of claim 9, wherein the program for computing the MTCSF image comprises a program for dividing each MTw signal by the reference MR signal.

12. A method for quantifying demyelination in a spinal cord, comprising:

acquiring an MTw image of the spinal cord, the MTw image having a plurality of voxels, wherein each voxel has a corresponding MR signal;

identifying a reference region of voxels within the plurality of voxels, wherein the region of voxels corresponds to cerebrospinal fluid;

computing a reference MR signal corresponding to the region of voxels; and

computing a normalized MT weighted image, based on the ratio of the MTw image and the reference MR signal.

13. The method of claim 12, further comprising identifying a hyperintensity signal region within a portion of the spinal cord that corresponds to white matter.

14. The method of claim 12, further comprising:

acquiring a conventional MR image of the spinal cord; and

comparing the normalized MT weighted image with the conventional MR image.

15. The method of claim 14, wherein comparing the normalized MT weighted image comprises co-registering the conventional MR image and the normalized MT weighted image.