System and method for embedded self-calibration within an inversion recovery pulse sequence
View Patent ↗An improved self-calibration method for accelerated magnetic resonance imaging (MRI) using inversion recovery pulse sequences allows calibration data for determining coil sensitivity profiles to be acquired by employing a calibration pulse sequence within the delay time of an inversion recovery pulse sequence. The calibration pulse sequence includes a constrained number of calibration pulses having small flip angles so that acceptable longitudinal magnetization recovery is provided.
1. A method for producing images with a magnetic resonance imaging (MRI) system, the steps comprising:
a) performing, with the MRI system, an inversion recovery pulse sequence including a delay time (TD) to acquire image data using accelerated imaging;
b) performing, with the MRI system, a calibration pulse sequence to acquire calibration data using unaccelerated imaging, wherein the calibration pulse sequence is embedded within the TD of the inversion recovery pulse sequence;
c) repeating, with the MRI system, steps a) and b) a plurality of times until a desired amount of image data and calibration data is acquired;
d) generating a plurality of coil sensitivity profiles from the acquired calibration data; and
e) reconstructing an image using the acquired image data and the sensitivity profiles produced in step d).
2. The method as recited in claim 1 wherein step b) further includes employing a series of calibration pulses having a selected flip angle.
3. The method as recited in claim 2 wherein the selected flip angle is less than five degrees.
4. The method as recited in claim 3 wherein the number of calibration pulses is constrained so that the number of calibration pulses multiplied by the repetition time between calibration pulses is less than the TD of the inversion recovery pulse sequence.
5. The method as recited in claim 1 wherein the inversion recovery pulse sequence of step a) is a magnetization prepared rapid gradient echo (MP-RAGE) pulse sequence.
6. The method as recited in claim 1 wherein the inversion recovery pulse sequence of step a) is a non-contrast magnetic resonance angiography pulse (MRA) pulse sequence.
7. The method as recited in claim 1 wherein the inversion recovery pulse sequence of step a) uses an inversion time selected to null cerebrospinal fluid.
8. A magnetic resonance imaging 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 plurality of gradient coils configured to apply a gradient field to the polarizing magnetic field;
a radio frequency (RF) system configured to apply an excitation field to the subject and acquire MR image data therefrom;
a computer system programmed to:
perform an inversion recovery pulse sequence including a delay time (TD) to acquire image data using accelerated imaging;
perform a calibration pulse sequence to acquire calibration data using unaccelerated imaging, wherein the calibration pulse sequence is embedded within the TD of the inversion recovery pulse sequence;
generate a plurality of coil sensitivity profiles from the acquired calibration data; and
reconstructing an image using the acquired image data and the sensitivity profiles.
9. The system as recited in claim 8 wherein the computer system is further programmed to employing a series of calibration pulses having a selected flip angle to perform the calibration pulse sequence.
10. The system as recited in claim 9 wherein the selected flip angle is less than five degrees.
11. The system as recited in claim 10 wherein the computer system is further programmed to constrain the number of calibration pulses so that the number of calibration pulses multiplied by the repetition time between calibration pulses is less than the TD of the inversion recovery pulse sequence.
12. The system as recited in claim 8 wherein the computer system is further programmed to perform a magnetization prepared rapid gradient echo (MP-RAGE) pulse sequence as part of the inversion recovery pulse sequence.
13. The system as recited in claim 8 wherein the computer system is further programmed to perform a non-contrast magnetic resonance angiography pulse (MRA) pulse sequence as part of the inversion recovery pulse sequence.
14. The system as recited in claim 8 wherein the computer system is further programmed to use an inversion time selected to null cerebrospinal fluid when performing the inversion recovery pulse sequence.