METHOD FOR QUANTITATIVELY MAPPING MYOCARDIAL CONTRACTILE FUNCTION WITH MAGNETIC RESONANCE BASED MULTIPARAMETRIC STRAIN ANALYSIS

• US 20090281415A1
• Filed: 01/08/2009
• Published: 11/12/2009
• Est. Priority Date: 01/09/2008
• Status: Active Grant

• Current Assignee: Washington University In St Louis
• Original Assignee: Washington University In St Louis
• Inventors: Pasque, Michael K., Cupps, Brian P.
• Granted Patent: US 9,176,211 B2
• Time in Patent Office: Days
• 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: G01R 33/5608 Data processing and visualization specially adapted for MR, e.g. for feature analysis and pattern recognition on the basis of measured MR data, segmentation of measured MR data, edge contour detection on the basis of measured MR data, for enhancing measured MR data in terms of signal-to-noise ratio by means of noise filtering or apodization, for enhancing measured MR data in terms of resolution by means for deblurring, windowing, zero filling, or generation of gray-scaled images, colour-coded images or images displaying vectors instead of pixels image data processing or generation, in general G06T
• 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

Abstract

The strain at different locations in a subject'"'"'s heart is determined by acquiring a series of MR images using a tagging pulse sequence (SPAMM) that produces a grid of lines in the reconstructed images. Circumferential strain, longitudinal strain, and the minimum principal strain angle, are all calculated at locations in the heart. These raw strain values are normalized by comparing them with corresponding values in a stored reference heart model. The normalized values at each location are combined to form a composite multiparametric strain index that is indicative of myocardial contractile function and these values are employed to modulate the color at corresponding locations in an anatomical image of the subject'"'"'s heart.

Claims

1. A method for producing an image indicative of myocardial contractile function with a magnetic resonance imaging (MRI) system, the steps comprising:

a) acquiring, with the MRI system, image data of a subject'"'"'s heart;

b) reconstructing images from the acquired image data;

c) calculating, from the reconstructed images, a plurality of strain values at each of a plurality of locations in the subject'"'"'s heart;

d) normalizing the calculated strain values using values in a stored reference heart model; and

e) producing from the normalized strain values an image indicative of myocardial contractile function.

2. The method as recited in claim 1 which includes:

f) combining normalized strain values at each of said locations to produce a multiparametric strain index; and

the image indicative of myocardial contractile function produced in step e) is an image of the subject'"'"'s heart in which the multiparametric strain index values are employed to modulate the color at said plurality of locations in the heart image.

3. The method as recited in claim 1 in which the plurality of strain values includes circumferential strain, longitudinal strain, and minimum principal strain angle.

4. The method as recited in claim 1 in which step a) employs a tagging pulse sequence that produces a grid of lines in the images reconstructed in step b) and the strain values are calculated in step c) by measuring the changes in the grid lines of images acquired at different cardiac phases.

5. The method as recited in claim 1 in which the stored reference model includes a mean strain value (μ

) at each heart location and a standard deviation value (σ

) at each heart location for each of said plurality of strain values, and a normalized strain (X_n) is calculated from the strain value (X) calculated in step c) according to the formula

X_n=(X−

μ

)/σ

.

6. The method as recited in claim 5 which includes:

f) combining the normalized strain values at each of said locations to produce a multiparametric strain index; and

the image indicative of myocardial viability produced in step e) is an image of the subject'"'"'s heart in which the strain index values are employed to modulate the color at corresponding locations in the heart image.

7. The method as recited in claim 6 in which the normalized strain values are combined in step f) by averaging their values.

8. The method as recited in claim 5 in which the stored reference model is produced by determining the strain values at said plurality of heart locations in a plurality of other subjects having normal myocardial contractile function and calculating the mean values (μ

) and the standard deviation values (σ

) therefrom.

9. The method as recited in claim 6 in which the normalized strain values to be combined in step f) are weighted differently.

10. The method as recited in claim 1 which further includes:

f) combining normalized strain values at each of said locations to produce a multiparametric strain index;

g) defining a plurality of regions in the heart; and

h) calculating a regional average strain index by averaging the multiparametric strain indices at locations within a region.

11. The method as recited in claim 1 which includes:

f) combining normalized strain values at each of said locations to produce a multiparametric strain index; and

the image indicative of myocardial contractile function produced in step e) includes;

e)i) producing an image of a heart model; and

e)ii) color coding pixels in the heart model image using the multiparametric strain index values.

12. The method as recited in claim 1 in which steps a) through d) are repeated to produce second normalized strain values, and the image produced in step e) is produced using the difference between the normalized strain values and the corresponding second normalized strain values.

13. The method as recited in claim 12 which further includes:

calculating a composite score by averaging the normalized strain values;

calculating a second composite score by averaging the second normalized strain values; and

comparing the second composite score with the composite score to indicate a change in myocardial contractile function.

14. The method as recited in claim 1 which further includes:

f) combining normalized strain values at each of said locations to produce a multiparametric strain index; and

g) calculating a composite score by averaging substantially all the multiparametric strain indices.

15. A method for producing an image indicative of myocardial contractile function with a magnetic resonance imaging (MRI) system, the steps comprising:

a) acquiring, with the MRI system, image data of a subject'"'"'s heart;

b) reconstructing images from the acquired image data;

c) calculating, from the reconstructed images, a plurality of strain values at each of a plurality of locations in the subject'"'"'s heart;

d) producing a normalized set of strain values by normalizing the calculated strain values using values in a stored reference heart model;

e) repeating steps a) through d) to produce a second set of normalized strain values; and

f) producing an image using the two sets of normalized strain values that is indicative of the change in myocardial contractile function.

16. The method as recited in claim 15 which includes combining normalized strain values at each of said locations to produce two sets of multiparametric strain indices, and step f) uses the two sets of multiparametric strain indices to produce this image.

17. The method as recited in claim 16 in which step f) includes:

f) i) subtracting one set of multiparametric strain indices from the other to produce a corresponding set of difference indices; and

f) ii) producing an image of the heart in which the difference indices are employed to modulate the color at corresponding locations in the heart image.