Format

Send to

Choose Destination
Magn Reson Med. 2015 Feb;73(2):857-64. doi: 10.1002/mrm.25152. Epub 2014 Apr 28.

Image reconstruction in k-space from MR data encoded with ambiguous gradient fields.

Author information

1
Medical Physics, Department of Radiology, University Medical Center Freiburg, Freiburg, Germany.

Abstract

PURPOSE:

In this work, the limits of image reconstruction in k-space are explored when non-bijective gradient fields are used for spatial encoding.

THEORY:

The image space analogy between parallel imaging and imaging with non-bijective encoding fields is partially broken in k-space. As a consequence, it is hypothesized and proven that ambiguities can only be resolved partially in k-space, and not completely as is the case in image space.

METHODS:

Image-space and k-space based reconstruction algorithms for multi-channel radiofrequency data acquisitions are programmed and tested using numerical simulations as well as in vivo measurement data.

RESULTS:

The hypothesis is verified based on an analysis of reconstructed images. It is found that non-bijective gradient fields have the effect that densely sampled autocalibration data, used for k-space reconstruction, provide less information than a separate scan of the receiver coil sensitivity maps, used for image space reconstruction. Consequently, in k-space only the undersampling artifact can be unfolded, whereas in image space, it is also possible to resolve aliasing that is caused by the non-bijectivity of the gradient fields.

CONCLUSION:

For standard imaging, reconstruction in image space and in k-space is nearly equivalent, whereas there is a fundamental difference with practical consequences for the selection of image reconstruction algorithms when non-bijective encoding fields are involved.

KEYWORDS:

PatLoc; gradient; k-space; magnetic resonance imaging; nonlinear; reconstruction

PMID:
24777559
PMCID:
PMC4617561
DOI:
10.1002/mrm.25152
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Wiley Icon for PubMed Central
Loading ...
Support Center