T2 contrast in magnetic resonance imaging with gradient echoes
First Claim
1. A method of acquiring MR images comprising the steps of:
- acquiring multiple sets of MR data from a series of read-out gradient pulses in a pulse sequence;
determining a nonlinear function of gradient echo time F(TE) to offset magnetic field inhomogeneities;
fitting the MR data to an equation that includes the nonlinear function F(TE); and
creating S(0) and T2 images using the results of the fitting step.
0 Assignments
0 Petitions
Accused Products
Abstract
A method and apparatus for acquiring MR images is disclosed. The technique allows rapid acquisition of T2 weighted MR images using gradient echo imaging, and also allows the acquisition of T1 weighted or spin density images, T2* or T2′ weighted images all from the same data set. The technique includes determining a nonlinear function of gradient echo time to offset magnetic field inhomogeneities and acquiring multiple sets of MR data from a series of read-out gradient pulses in a pulse sequence. Both 2-D and 3-D pulse sequence embodiments are disclosed. The MR data is then fit to an equation that includes the nonlinear function and the images are reconstructed that include T1 or spin density weighting, T2 weighting images, T2*, or T2′ weighting. The resulting images are naturally co-registered.
46 Citations
30 Claims
-
1. A method of acquiring MR images comprising the steps of:
-
acquiring multiple sets of MR data from a series of read-out gradient pulses in a pulse sequence;
determining a nonlinear function of gradient echo time F(TE) to offset magnetic field inhomogeneities;
fitting the MR data to an equation that includes the nonlinear function F(TE); and
creating S(0) and T2 images using the results of the fitting step. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
-
-
8. The method of claim 7 further comprising approximating the generalized equation to one of:
-
9. The method of claim 7 further comprising approximating the generalized equation to:
-
where Δ
ω
is a frequency difference across a voxel.
-
-
10. The method of claim 7 further comprising approximating the generalized equation to:
-
11. The method of claim 1 wherein the equation that includes the nonlinear function is:
-
12. The method of claim 1 wherein the equation that includes the nonlinear function accounts for both macroscopic and mesoscopic field inhomogeneities and is given by:
-
13. The method of claim 1 wherein the S(x,y;
- 0) image is one of a spin density image and a T1 weighted image.
-
14. An MRI apparatus to rapidly acquire T2 weighted MR images using gradient echo imaging comprising:
-
a magnetic resonance imaging (MRI) system having a plurality of gradient coils positioned about a bore of a magnet to impress a polarizing magnetic field, an RF transceiver system, and an RF switch controlled by a pulse module to transmit and receive RF signals to and from an RF coil assembly to acquire MR images; and
a computer programmed to;
acquire multiple sets of MR data from a series of read-out gradient pulses in a pulse sequence;
determine signal intensity for each MR data;
fit the MR data to a signal magnitude equation that includes a nonlinear function; and
reconstruct T2 weighted MR images that are substantially free of magnetic field inhomogeneities. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
-
-
19. The MRI apparatus of claim 18 wherein the computer program approximates the generalized equation to one of:
-
20. The MRI apparatus of claim 18 wherein the computer program approximates the generalized equation to:
-
where Δ
ω
is a frequency difference across a voxel.
-
-
21. The MRI apparatus of claim 18 wherein the computer program approximates the generalized equation to:
-
22. The MRI apparatus of claim 14 further comprising:
-
a computer readable memory unit having stored therein a number of models for the nonlinear function;
a user input to receive an input identifying an object scanned; and
wherein the computer is further programmed to determine a model for the nonlinear function based on the object scanned.
-
-
23. The MRI apparatus of claim 14 wherein the MR images reconstructed are co-registered.
-
24. A computer program for use with an MRI apparatus comprising instructions which, when executed by a computer, cause the computer to:
-
apply a pulse sequence with a train of gradient read-out pulses;
acquire MR data during the train of gradient read-out pulses;
depending upon identification of an object scanned, determine a nonlinear function of gradient echo time;
fit signal magnitude of the MR data to a signal magnitude equation;
reconstruct MR images using results of the fit wherein the MR images reconstructed can include S(0) and T2 weighted images. - View Dependent Claims (25, 26, 27, 28, 29, 30)
-
Specification