Method for measuring myocardial motion and the like

• US 6,171,241 B1
• Filed: 06/11/1998
• Issued: 01/09/2001
• Est. Priority Date: 06/12/1997
• Status: Expired due to Term

• Current Assignee: Johns Hopkins University, Ncneil-Ppc Incorporated
• Original Assignee: Johns Hopkins University
• Inventors: McVeigh, Elliot R., Bolster, Bradley D. Jr.
• Primary Examiner(s): Casler, Brian L.
• Application Number:
  US09/095,910
• Time in Patent Office: 943 Days
• Field of Search: 600/410, 600/413, 324/307, 324/309, 382/128, 382/107, 128/922
• US Class Current: 600/410
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/1128 using image analysis A61B5/1127 takes precedence
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: G01R 33/563 of moving material, e.g. flow contrast angiography
• CPC Class Codes: G01R 33/56333 Involving spatial modulation of the magnetization within an imaged region, e.g. spatial modulation of magnetization [SPAMM] tagging perfusion imaging based on arterial spin tagging G01R33/56366
• CPC Class Codes: G01R 33/5673 Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker

Abstract

A method of magnetic resonance imaging of myocardial motion includes positioning a portion of a patient such as a patient'"'"'s heart within a main magnetic field and employing a plurality of RF signals to establish a plurality of parallel plane tags through the portion. In imaging heart motion, a first minimum spacing between adjacent tags is employed in a region where the tags will decrease their separation over systole and a second initial tag separation will be employed for portions wherein the tags increase their separation over systole. The method facilitates simultaneous imaging of both such motions. Fourier coefficients may be employed in establishing the generally parallel tags which may be positioned generally symmetrically about a central tag.

Claims

1. A method of magnetic resonance imaging motion of a portion of a patient comprising

positioning a patient'"'"'s heart within a main magnetic field,

employing a plurality of RF pulses to establish a plurality of parallel plane tags through said portion,

employing a first spacing between adjacent said tags in a first region,

establishing a second minimum spacing between adjacent said tags in a second region, and

said first spacing being different from said second minimum spacing.

2. The method of claim 1 including

employing said method in measuring myocardial motion.

3. The method of claim 2 including

establishing said plurality of parallel plane tags through the myocardium.

4. The method of claim 3 including

employing said first spacing in said first region where said tags decrease their separation over systole, and

employing said second minimum spacing in said second region where said tags increase their separation over systole.

5. The method of claim 4 including

employing said method where said first minimum spacing is employed in connection with imaging circumferential shortening, and

employing said second minimum spacing in a region sampling radial thickening of said myocardium.

6. The method of claim 5 including

effecting said imaging of said circumferential shortening and said radial thickening substantially simultaneously.

7. The method of claim 6 including

said first spacing being of greater magnitude than said second minimum spacing.

8. The method of claim 7 including

establishing said plurality of parallel plane tags with generally symmetrical spacing about a central said tag.

9. The method of claim 6 including

employing at least two tag separation sizes in said first spacing.

10. The method of claim 9 including

employing at least two tag separation sizes in said second minimum spacing.

11. The method of claim 10 including

employing separations of about 4 to 6 mm in said second minimum spacing.

12. The method of claim 9 including

employing separations of about 4 to 6 mm in said first spacing.

13. The method of claim 1 including

employing a multi-spectral radio-frequency pulse as said RF pulse.

14. The method of claim 13 including

providing a constant gradient pulse during said RF pulse applied generally normal to said tag planes.

15. The method of claim 1 including

creating said tag spacing by generating Fourier coefficients of the variable spaced tag planes and employing said coefficients to construct said RF pulses.

16. The method of claim 15 including

employing as said Fourier coefficients, coefficients determined by the following equations:

$a_0=\frac{1}{2<br><br>L}<br><br>\left(2<br><br>J+1\right)$$a_n=\frac{1}{L}<br><br>\left(1+2<br><br>\underset{j=1}{\overset{J}{\sum <br><br>}}<br><br>\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\frac{n<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>x_j}{L}\right)\right),n=1,\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>},N$

wherein a₀ represents the amplitude of the first RF pulse, a_n represents the amplitude of the RF pulse train and “

_n”

indicates the number of a given pulse, x_j is the position of an individual tag with respect to the center of the tagging pattern, J represents the individual tags on either side of the center tag, L is the length of one side of the tagging pattern, and N+1 is the total number of pulses.

17. The method of claim 16 including

establishing a symmetric distribution of RF pulses in accordance with the relationship of claim 15 wherein $\frac{-N}{2}\le$

n≤

N2,

18. The method of claim 1 including

employing as said first spacing about 4 to 6 mm, and

effecting smaller spacing between at least some adjacent parallel tags of said tags having said second minimum spacing.

19. The method of claim 18 including

said tags being spaced symmetrically about a central tag.

20. The method of claim 1 including

employing a train of non-selective RF pulses as said RF pulses.

21. The method of claim 20 including

providing gradient pulses separating said non-selective components of said RF pulses.