Partial fourier shells trajectory for non-cartesian MRI.

Phys Med Biol 2019 02 6;64(4):04NT01. Epub 2019 Feb 6.

Mayo Clinic, 200 First Street SW, Rochester, MN 55905, United States of America.

Non-Cartesian MRI acquisition has demonstrated various advantages in many clinical applications. The shells trajectory is a 3D non-Cartesian MRI acquisition technique that samples the k-space using a series of concentric shells to achieve efficient 3D isotropic acquisition. Partial Fourier acquisition is an acceleration technique that is widely used in Cartesian MRI. It exploits the conjugate symmetry of k-space measurement to reduce the number of k-space samples compared to full-k-space acquisition, without loss of spatial resolution. For a Cartesian MRI acquisition, the direction of partial Fourier acceleration is aligned either with the phase encoded or frequency encoded direction. In those cases, the underlying image matrix can be reconstructed from the undersampled k-space data using a non-iterative, homodyne reconstruction framework. However, designing a non-Cartesian acquisition trajectory that is compatible with non-iterative homodyne reconstruction is not nearly as straightforward as in the Cartesian case. One reason is the non-iterative homodyne reconstruction requires (slightly over) half of the k-space to be fully sampled. Since the direction of partial Fourier acceleration varies throughout the acquisition in the non-Cartesian trajectory, directly applying the same partial Fourier acquisition pattern (as in Cartesian acquisitions) to a non-Cartesian trajectory does not necessarily yield a continuous, physically-achievable trajectory. In this work, we develop an asymmetric shells trajectory with fully-automated trajectory and gradient waveform design to achieve partial Fourier acquisition for the shells trajectory. We then demonstrate a non-iterative image reconstruction framework for the proposed trajectory. Phantom and in vivo brain scans based on spoiled gradient echo (SPGR) shells and magnetization-prepared shells (MP-shells) were performed to test the proposed trajectory design and reconstruction method. Our phantom and in vivo results demonstrate that the proposed partial Fourier shells trajectory maintains the desirable image contrast and high sampling efficiency from the fully sampled shells, while further reducing data acquisition time.

Download full-text PDF

Source
http://dx.doi.org/10.1088/1361-6560/aafcc5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6454926PMC
February 2019
8 Reads

Publication Analysis

Top Keywords

partial fourier
28
shells trajectory
20
non-iterative homodyne
12
non-cartesian mri
12
fourier acquisition
12
mri acquisition
12
trajectory
12
homodyne reconstruction
12
acquisition
11
shells
9
non-cartesian trajectory
8
direction partial
8
proposed trajectory
8
fully sampled
8
phantom vivo
8
fourier acceleration
8
reconstruction framework
8
trajectory non-cartesian
8
cartesian mri
8
fourier shells
8

References

(Supplied by CrossRef)

Bernstein M A et al.
Handbook of MRI Pulse Sequences 2004

Similar Publications