Systems and methods for efficient trajectory optimization in magnetic resonance fingerprinting

Patent metadata

Field	Value
Publication number	US-10466321-B2
Application number	US-201615294989-A
Country	US
Kind code	B2
Filing date	Oct 17, 2016
Priority date	Nov 12, 2015
Publication date	Nov 5, 2019
Grant date	Nov 5, 2019

Abstract

Systems and methods for acquiring magnetic resonance fingerprinting (MRF) data includes performing a schedule optimization that sequentially selects discrimination at each trajectory to yield an optimal trajectory and controlling a magnetic resonance imaging (MRI) system to perform a pulse sequence using the optimal trajectory to acquire MRF data. The process also includes estimating quantitative parameters of the subject using the MRF data by comparing the MRF data to a dictionary database and generating a map of quantitative parameters of the subject using the estimated quantitative parameters of the subject and the MRF data.

First claim

The invention claimed is:

1. A magnetic resonance imaging (MRI) system, comprising:
a magnet system configured to generate a polarizing magnetic field about at least a portion of a subject arranged in the MRI system;
a magnetic gradient system including a plurality of magnetic gradient coils configured to apply at least one magnetic gradient field to the polarizing magnetic field;
a radio frequency (RF) system configured to apply an RF field to the subject and to receive magnetic resonance signals from the subject using a coil array;
a computer system programmed to:
(i) perform a deterministic schedule optimization method to select pulse sequence parameters that minimize schedule lengths needed to fully sample k-space with each repetition time (TR) of the pulse sequence;
(ii) control the MRI system to acquire magnetic resonance fingerprinting (MRF) data from the subject by performing the pulse sequence;
(iii) estimate quantitative parameters of the subject using the MRF data by comparing the MRF data to a dictionary database; and
(iv) generate a map of quantitative parameters of the subject using the estimated quantitative parameters of the subject and the MRF data.

2. The system of claim 1 wherein the computer system is further programmed to sequentially select the pulse sequence parameters to direct the MRI system to generate a plurality of different signal evolutions that maximize discrimination between different quantitative parameters in a selected number of repetition time (TR) periods.

3. The system of claim 2 wherein the computer system is further programmed to control the MRI system to perform a plurality of successive cycles of the pulse sequence using the selected pulse sequence parameters and wherein the MRF data represents the plurality of different signal evolutions that maximize discrimination between different quantitative parameters.

4. The system of claim 2 wherein the computer system is further programmed to minimize an objective function that simulates the acquisition parameters and compute a matrix that is based on estimated values of the pulse sequence parameters and the quantitative parameters to sequentially select the pulse sequence parameters.

5. The system of claim 4 wherein the computer system is further programmed to select initial estimates of the pulse sequence parameters and form the matrix based on the initial estimates.

6. The system of claim 4 wherein the matrix comprises a first matrix that defines a dot product between a second matrix and a transpose of the second matrix, and wherein the second matrix includes estimates of the pulse sequence parameters and simulated values for the quantitative parameters.

7. The system of claim 4 wherein the computer system is further programmed to minimize the objective function by searching for the pulse sequence parameters that minimize a difference between a sum of off-diagonal elements of the matrix and a sum of on-diagonal elements of the matrix.

8. The system of claim 1 wherein the computer system is further programmed to perform the pulse sequence to maintain residual transverse magnetization through a delay period performed between successive cycles of the pulse sequence, wherein the delay period is selected to allow spins of different tissue types within the subject to evolve differently as a function of tissue parameters within the different tissue types during the delay period.

9. A method for generating a map of quantitative parameters of a subject using a magnetic resonance imaging (MRI) system, the method including steps comprising:
(i) performing a schedule creation that sequentially selects discrimination at each time step to yield a preferred schedule;
(ii) controlling the MRI system to perform a pulse sequence using the preferred schedule to acquire magnetic resonance fingerprinting (MRF) data;
(ii) estimating quantitative parameters of the subject using the MRF data by comparing the MRF data to a dictionary database; and
(iii) generating a map of quantitative parameters of the subject using the estimated quantitative parameters of the subject and the MRF data.

10. The method of claim 9 wherein (ii) further includes acquiring a first portion of the MRF data by fully sampling k-space, line-by-line, using a first flip angle (FA) and first repetition time (TR) and acquiring a second portion of the MRF data by fully sampling k-space, line-by-line, using a second FA and second TR and wherein at least one of the second FA or the second TR are different from the first FA and first TR.

11. The method of claim 9 wherein the MRF data is acquired using a first flip angle and a second flip angle that are different flip angles.

12. The method of claim 9 wherein the dictionary database accounts for steady-state MRF data acquisition.

13. A method for generating a map of quantitative parameters of a subject using a magnetic resonance imaging (MRI) system, the method including steps comprising:
(i) performing a deterministic schedule optimization method to select pulse sequence parameters that minimize schedule lengths needed to fully sample k-space with each repetition time (TR) of the pulse sequence;
(ii) controlling the MRI system to acquire magnetic resonance fingerprinting (MRF) data from the subject by performing the pulse sequence;
(iii) estimating quantitative parameters of the subject using the MRF data by comparing the MRF data to a dictionary database; and
(iv) generating a map of quantitative parameters of the subject using the estimated quantitative parameters of the subject and the MRF data.

14. The method of claim 13 wherein the pulse sequence includes maintaining residual transverse magnetization through a delay period performed between successive cycles of the pulse sequence, wherein the delay period is selected to allow spins of different tissue types within the subject to evolve differently as a function of tissue parameters within the different tissue types during the delay period.

15. The method of claim 13 wherein step (i) further includes sequentially selecting the pulse sequence parameters that are selected to direct the MRI system to generate a plurality of different signal evolutions that maximize discrimination between different quantitative parameters in a selected number of repetition time (TR) periods.

16. The method of claim 15 wherein step (ii) includes acquiring the MRF data with the MRI system by directing the MRI system to perform a plurality of successive cycles of the pulse sequence using the selected pulse sequence parameters, the MRF data representing the plurality of different signal evolutions that maximize discrimination between different quantitative parameters.

17. The method of claim 15 wherein sequentially selecting the pulse sequence parameters includes minimizing an objective function that simulates the pulse sequence parameters and computed a matrix that is based on estimated values of the acquisition parameters and the quantitative parameters to be estimated.

18. The method of claim 17 further comprising selecting initial estimates of the pulse sequence parameters and forming the matrix based on the initial estimates.

19. The method of claim 17 wherein the matrix comprises a first matrix that defines a dot product between a second matrix and a transpose of the second matrix, wherein the second matrix includes estimates of the pulse sequence parameters and simulated values for the quantitative parameters.

20. The method of claim 17 wherein the objective function is minimize

Assignees

• Massachusetts Gen Hospital

Inventors

• Cohen Ouri

Classifications

• G01R33/4818 Primary

  MR characterised by data acquisition along a specific k-space trajectory or by the temporal order of k-space coverage, e.g. centric or segmented coverage of k-space · CPC title

• G01R33/243

  Spatial mapping of the polarizing magnetic field · CPC title

• G01R33/50

  based on the determination of relaxation times {, e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences} · CPC title