Artifact due to B0 fluctuations in fMRI: Correction using the k-space central line

• Published in: Magnetic resonance in medicine Vol. 46; no. 1; pp. 198 - 201
• Main Authors: Durand, Emmanuel, van de Moortele, Pierre-François, Pachot-Clouard, Mathilde, Le Bihan, Denis
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 01.07.2001; Williams & Wilkins
• Subjects: B0 stability; Biological and medical sciences; EPI; fMRI; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Miscellaneous. Technology; navigator echo; Nervous system; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Evaluation; Fluctuations; Central nervous system; Signal processing; Medical imagery; Artefact; Error correction; Technique; Magnetic field; Nuclear magnetic resonance imaging; Brain (vertebrata); Test object
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.1177

Magnetic resonance experiments require the main magnetic field, B0, to remain very stable. Several external sources, such as moving ferromagnetic objects and/or changing electromagnetic fields, can significantly change the value of B0 over time. This work describes an apparent displacement along the phase‐encoding axis caused by a variation in B0. This artifact was observed in fMRI images acquired with EPI. The effect was characterized and tested using an immobile phantom. The image displacement motion along the phase‐encoding axis closely followed the changes in B0. The phase of the central line in the Fourier space was successfully used to correct this artifact. Fluctuations in B0 may result in artifacts that mimic subject head motion, and must be appropriately corrected. Magn Reson Med 46:198–201, 2001. © 2001 Wiley‐Liss, Inc.