MULTI-CONTRAST DELAYED ENHANCEMENT CARDIAC MAGNETIC RESONANCE IMAGING

• US 20090275822A1
• Filed: 05/01/2008
• Published: 11/05/2009
• Est. Priority Date: 05/01/2008
• Status: Active Grant

• Current Assignee: Sunnybrook Health Sciences Centre
• Original Assignee: Sunnybrook Health Sciences Centre
• Inventors: Detsky, Jay S., Wright, Graham A.
• Granted Patent: US 9,395,431 B2
• Time in Patent Office: Days
• US Class Current: 600/413
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence
• CPC Class Codes: G01R 33/50 based on the determination of relaxation times , e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences
• CPC Class Codes: G01R 33/5601 involving use of a contrast agent for contrast manipulation, e.g. a paramagnetic, super-paramagnetic, ferromagnetic or hyperpolarised contrast agent
• CPC Class Codes: G01R 33/5602 by filtering or weighting based on different relaxation times within the sample, e.g. T1 weighting using an inversion pulse
• CPC Class Codes: G01R 33/5614 using a fully balanced steady-state free precession [bSSFP] pulse sequence, e.g. trueFISP
• CPC Class Codes: G01R 33/56325 Cine imaging
• 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 33/5673 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 series of MR image frames are acquired that depict a subject'"'"'s heart at successive cardiac phases. Delayed enhancement of infarcted myocardium is depicted in some of the image frames by administering a contrast agent prior to data acquisition. Data acquisition is performed in a single breath hold by producing an RF inversion pulse followed by segments of SSFP pulse sequences during a succession of cardiac gated heart beats. The acquired MR image frames depict contrast between blood, viable myocardium and nonviable myocardium, and they depict left ventricle wall thickness and wall thickening throughout the cardiac cycle.

Claims

1. A method for producing a series of cardiac gated magnetic resonance images of a subject'"'"'s heart, the steps comprising:

a) administering a contrast agent to the subject;

b) producing a gating signal that indicates the start of the subject'"'"'s cardiac cycle;

c) producing an RF inversion pulse that inverts spin magnetization throughout a field of view a preset time after a gating signal is produced;

d) acquiring a series of MR data segments at successive cardiac phases after the RF inversion pulse is produced using a plurality of steady-state free precession pulse sequences (SSFP);

e) repeating steps b) through d) until sufficient k-space data is acquired by the SSFP pulse sequences in each segment from which an image frame can be reconstructed for each segment; and

f) reconstructing a series of image frames depicting the heart at a succession of cardiac phases using the k-space data acquired in the series of segments.

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

g) performing a magnetization equalization pulse sequence during a cardiac cycle preceding the first acquisition of MR data segments.

3. The method as recited in claim 1 in which the preset time interval in step c) is selected such that images that depict optimal contrast between viable and nonviable myocardium tissues of the heart are acquired during the mid-diastole of each cardiac cycle.

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

h) producing a T₁* map by fitting the magnitude values at corresponding pixels in the series of image frames to a T₁* curve and setting the magnitude of the corresponding pixel in the T₁* map to the T₁* value determined by the T₁* curve.

5. The method as recited in claim 1 in which the number of SSFP pulse sequences in each segment is selected such that sufficient k-space data is acquired to reconstruct an image frame for each segment by performing step e) during a single breath hold of the subject.

6. A method for producing a series of delayed contrast enhanced magnetic resonance images of a subject'"'"'s heart, the steps comprising:

a) producing a gating signal that indicates the start of the subject'"'"'s cardiac cycle;

b) producing an RF inversion pulse that inverts spin magnetization throughout a field of view a preset time after a gating signal is produced;

c) acquiring a series of MR data segments at successive cardiac phases after the RF inversion pulse is produced using a plurality of steady-state free precession pulse sequences (SSFP);

d) repeating steps a) through c) until sufficient k-space data is acquired by the SSFP pulse sequences in each segment from which an image frame can be reconstructed for each segment; and

e) reconstructing a series of image frames depicting the heart at a succession of cardiac phases using the k-space data acquired in the series of segments.

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

f) performing a magnetization equalization pulse sequence during a cardiac cycle preceding the first acquisition of MR data segments.

8. The method as recited in claim 6 in which the preset time interval in step b) is selected such that images that depict best contrast between viable and nonviable myocardium tissues of the heart are acquired during the mid-diastole of each cardiac cycle.

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

g) producing a T₁* map by fitting the magnitude values at corresponding pixels in the series of image frames to a T₁* curve and setting the magnitude of the corresponding pixel in the T₁* map to the calculated T₁* value determined by the T₁* curve.

10. The method as recited in claim 6 in which the number of SSFP pulse sequences in each segment is selected such that sufficient k-space data is acquired to reconstruct an image frame for each segment by performing step e) during a single breath hold of the subject.

11. A method for determining the health of a subject'"'"'s heart, the steps comprising:

a) acquiring a series of image frames of the heart with a magnetic resonance imaging system (MRI) by performing a scan which includes;

a)i) administering a contrast agent to the subject;

a)ii) performing a cardiac gated, segmented acquisition during each of a series of cardiac cycles and after the application of an inversion RF pulse during each cardiac cycle to acquire a corresponding series of image frame data sets having tissue contrast that differs as a function of recovery time (TI) after the inversion RF pulse; and

a)iii) reconstructing a series of image frames from the corresponding image frame data sets;

b) produce a T₁* map indicating the inversion recovery time of tissues depicted in the image frames; and

c) producing a steady state (ss) map indicating the fully recovered signal value of tissues depicted in the image frames.

12. The method as recited in claim 11 in which step a)ii) is performed using a steady state free precession (SSFP) pulse sequence to direct the MRI system.

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

d) selecting from the series of image frames one or more image frames that depicts optimal contrast between infarcted myocardium tissue and normal myocardium tissue.

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

e) producing a segmented image frame by using the T₁* map and the ss map as input to a fuzzy clustering process.

15. The method as recited in claim 14 in which the image frame is segmented to indicate normal myocardial tissues, infarcted myocardial tissues and blood.

16. The method as recited in claim 15 in which the three segmented tissues are indicated by color coding image frame pixels.

17. The method as recited in claim 11 in which step b) includes:

b)i) selecting a set of the reconstructed image frames that depict the recovery of signals at each location therein over a period of time following the inversion RF pulse;

b)ii) fitting recovery curves to the signals at corresponding locations in the selected image frames; and

b)iii) calculating a T₁* value for each image frame location from the recovery curve for that location.

18. The method as recited in claim 17 in which step c) includes calculating the steady state value ss for each image frame location from the recovery curve for that location.

19. The method as recited in claim 17 in which step b)i) further includes registering the selected image frames to align tissues in the depicted subject at substantially the same image frame locations in all the selected image frames.