Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
. 1999;8(2-3):80-5.
doi: 10.1002/(sici)1097-0193(1999)8:2/3<80::aid-hbm2>3.0.co;2-c.

Sources of distortion in functional MRI data

P Jezzard  1 , S Clare
Affiliations
Review

Sources of distortion in functional MRI data

P Jezzard et al. Hum Brain Mapp. 1999.

Abstract

Functional magnetic resonance image (fMRI) experiments rely on the ability to detect subtle signal changes in magnetic resonance image time series. Any areas of signal change that correlate with the neurological stimulus can then be identified and compared with a corresponding high-resolution anatomical scan. This report reviews some of the several artefacts that are frequently present in fMRI data, degrading their quality and hence their interpretation. In particular, the effects of magnetic field inhomogeneities are described, both on echo planar imaging (EPI) data and on spiral imaging data. The modulation of these distortions as the subject moves in the magnet is described. The effects of gradient coil nonlinearities and EPI ghost correction schemes are also discussed.

PubMed Disclaimer

References

    1. Ahn CB, Kim JH, Cho ZH. 1986. High speed spiral‐scan echo planar NMR imaging—I. IEEE Trans Med Imag MI‐5:2–7. - PubMed
    1. Irarrazabal P, Meyer CH, Nishimura DG, Macovski A. 1996. Inhomogeneity correction using an estimated linear field map. Magn Reson Med 35:278–282. http://www.ncbi.nlm.nih.gov:80/htbin-post/Entrez/query?uid=96208355&form... - PubMed
    1. Jezzard P, Balaban RS. 1995. Correction for geometric distortion in echo planar images from B0 field variations. Magn Reson Med 34:65–73. http://www.ncbi.nlm.nih.gov:80/htbin-post/Entrez/query?uid=95405234&form... - PubMed
    1. Mansfield P. 1977. Multi‐planar image formation using NMR spin echoes. J Phys C 10:L55–L58.
    1. Meyer CH, Macovski A. 1987. Square spiral fast imaging: interleaving and off‐resonance effects. Proc 6th Soc Magn Reson Med 1:230.