Parallel magnetic resonance imaging method using a radial acquisition trajectory
A fast and efficient method for reconstructing an image from undersampled, parallel MRI data sets acquired with non-Cartesian trajectories includes the calculation of unsampled k-space data from the acquired k-space data and sets of calculated reconstruction coefficients. To reduce the computation time, only a few reference reconstruction coefficients are calculated using a matrix inversion step and the remaining reconstruction coefficients are produced by interpolating between the reference reconstruction coefficients.
1. A method for producing an image with a magnetic resonance imaging (MRI) system, the steps comprising:
a) acquiring in parallel a plurality of undersampled k-space data sets with the MRI system using a pulse sequence that samples k-space along non-Cartesian trajectories;
b) reconstructing coil images from the plurality of undersampled k-space data sets;
c) producing coil sensitivity maps using the coil images;
d) calculating a set of reference reconstruction coefficients for a coil using the undersampled coil k-space data and the coil sensitivity maps;
e) calculating additional reconstruction coefficients by interpolating between calculated reference reconstruction coefficients;
f) calculating additional k-space data for the undersampled k-space data set for the coil using the reference reconstruction coefficients and the additional reconstruction coefficients to form a complete coil k-space data set;
g) repeating steps d), e) and f) for each coil to produce corresponding complete coil k-space data sets;
h) reconstructing final coil images from the complete coil k-space data sets; and
i) producing the image by combining the final coil images produced in step h).
2. The method as recited in claim 1 in which the coil images are combined in step i) by calculating the square root of the sum of the squares of corresponding values in the coil images.
3. The method as recited in claim 1 in which the non-Cartesian trajectory is a radial trajectory.
4. The method as recited in claim 1 in which step b) reconstructs coil images using a central region of k-space data in the undersampled k-space data sets.
5. The method as recited in claim 4 in which step c) includes:
c)i) reconstructing additional coil images using all the k-space data in the plurality of undersampled k-space data sets;
c)ii) combining the additional coil images to form a composite image; and
c)iii) producing each coil sensitivity map by dividing the corresponding coil image by the composite image.