System and method for dynamic, cardiac phase-resolved quantitative longitudinal relaxation parameter mapping

1. A method for producing a map of a longitudinal relaxation parameter for a tissue of a subject using a magnetic resonance imaging (MRI) system, the steps of the method comprising:

(a) establishing a selected magnetization state in the tissue of the subject using the MRI system;

(b) after the selected magnetization state is established, applying a T1-preparation RF pulse to generate inverted magnetization in the tissue of the subject;

(c) while the inverted magnetization in the tissue of the subject is recovering and until the selected magnetization state is established again, acquiring a data set at each of a plurality of different cardiac phases by sampling k-space in a k-space segment;

(d) repeating steps (b) and (c) for a selected number of inversion recovery periods such that a plurality of data sets are acquired for each of the plurality of different cardiac phases;

(e) reconstructing images from the plurality of data sets;

(f) producing the map of the longitudinal relaxation parameter by fitting the images to a parametric signal model that at least includes a parameter associated with the longitudinal relaxation parameter and another parameter associated with an inversion efficiency; and

wherein step (f) includes jointly estimating the longitudinal relaxation parameter map and a transmit RF field (B1+) map by fitting the images to the parametric signal model.

2. The method as recited in claim 1 , wherein the T1-preparation RF pulse is applied at a time based on a detection of a physiological trigger event.

3. The method as recited in claim 2 , wherein the physiological trigger event is an occurrence of an R-wave in an electrocardiograph (ECG) signal measured from the subject.

4. The method as recited in claim 3 , wherein the T1-preparation RF pulse is applied when the R-wave in the ECG signal is detected.

5. The method as recited in claim 1 , wherein the selected magnetization state is a pulsed steady-state and is established in step (a) by applying a series of continuous RF pulses to the tissue of the subject.

6. The method as recited in claim 5 , wherein the series of continuous RF pulses comprises RF pulses having a flip angle less than 180 degrees.

7. The method as recited in claim 6 , wherein the series of continuous RF pulses comprises RF pulses having a flip angle in a range of 1 to 20 degrees.

8. The method as recited in claim 1 , wherein data in each data set are acquired by sampling k-space in the k-space segment using a data acquisition comprising a series of continuous RF pulses and a spoiled gradient readout.

9. The method as recited in claim 8 , wherein the series of continuous RF pulses comprises RF pulses having a flip angle less than 180 degrees.

10. The method as recited in claim 9 , wherein the series of continuous RF pulses comprises RF pulses having a flip angle in a range of 1 to 20 degrees.

11. The method as recited in claim 1 , wherein step (c) further includes after acquiring each data set, applying a selected number of dummy RF pulses until a physiological trigger event is detected.

12. The method as recited in claim 11 , wherein the physiological trigger event is an occurrence of an R-wave in an electrocardiograph (ECG) signal measured from the subject.

13. The method as recited in claim 11 , wherein no data are acquired in response to the dummy RF pulses.

14. The method as recited in claim 1 , wherein step (c) includes acquiring each data set for each of the plurality of different cardiac phases by sampling k-space in a different k-space segment.

15. The method as recited in claim 1 , wherein the B1+ map is estimated based on the parameter associated with the inversion efficiency.

16. The method as recited in claim 1 , wherein the T1-preparation RF pulse is an RF inversion pulse.

17. The method as recited in claim 1 , wherein the selected magnetization state is one of a pulsed steady-state, a thermal equilibrium, or a desired level of saturation.

18. The method as recited in claim 1 , wherein step (f) includes producing a plurality of longitudinal relaxation parameter maps.

19. The method as recited in claim 18 , wherein the plurality of longitudinal relaxation parameter maps are temporally resolved longitudinal relaxation parameter maps.

20. The method as recited in claim 1 , wherein step (e) includes reconstructing the images using an iterative reconstruction that is regularized in part using a multi-scale locally low-rank noise reduction.

21. The method as recited in claim 1 , wherein step (e) includes reconstructing the images using an iterative reconstruction that is regularized in part using a low-rank tensor regularization.

22. A method for producing a map of a longitudinal relaxation parameter for a tissue of a subject using a magnetic resonance imaging (MRI) system, the steps of the method comprising:

(a) establishing a selected magnetization state in the tissue of the subject using the MRI system;

(b) after the selected magnetization state is established, applying a T1-preparation RF pulse to generate inverted magnetization in the tissue of the subject;

(c) while the inverted magnetization in the tissue of the subject is recovering and until the selected magnetization state is established again, acquiring a data set at each of a plurality of different cardiac phases by sampling k-space in a k-space segment;

(d) repeating steps (b) and (c) for a selected number of inversion recovery periods such that a plurality of data sets are acquired for each of the plurality of different cardiac phases;

(e) reconstructing images from the plurality of data sets;

(f) producing the map of the longitudinal relaxation parameter by fitting the images to a parametric signal model that at least includes a parameter associated with the longitudinal relaxation parameter and another parameter associated with an inversion efficiency;

wherein the selected magnetization state is a pulsed steady-state and is established in step (a) by applying a series of continuous RF pulses to the tissue of the subject; and

wherein the series of continuous RF pulses comprises RF pulses having a flip angle in a range of 1 to 20 degrees.

23. A method for producing a map of a longitudinal relaxation parameter for a tissue of a subject using a magnetic resonance imaging (MRI) system, the steps of the method comprising:

(a) establishing a selected magnetization state in the tissue of the subject using the MRI system;

(b) after the selected magnetization state is established, applying a T1-preparation RF pulse to generate inverted magnetization in the tissue of the subject;

(c) while the inverted magnetization in the tissue of the subject is recovering and until the selected magnetization state is established again, acquiring a data set at each of a plurality of different cardiac phases by sampling k-space in a k-space segment;

(d) repeating steps (b) and (c) for a selected number of inversion recovery periods such that a plurality of data sets are acquired for each of the plurality of different cardiac phases;

(e) reconstructing images from the plurality of data sets;

(f) producing the map of the longitudinal relaxation parameter by fitting the images to a parametric signal model that at least includes a parameter associated with the longitudinal relaxation parameter and another parameter associated with an inversion efficiency;

wherein data in each data set are acquired by sampling k-space in the k-space segment using a data acquisition comprising a series of continuous RF pulses and a spoiled gradient readout,

wherein the series of continuous RF pulses comprises RF pulses having a flip angle in a range of 1 to 20 degrees.