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PURPOSE: Magnetic field fluctuations caused by subject motion, such as breathing or limb motion, can degrade image quality in brain MRI, especially at high field strengths. The purpose of this study was to investigate the feasibility of retrospectively correcting for such physiological field perturbations based on concurrent field monitoring. THEORY AND METHODS: High-resolution T2*-weighted gradient-echo images of the brain were acquired at 7T with subjects performing different breathing and hand movement patterns. Field monitoring with a set of (19) F NMR probes distributed around the head was performed in two variants: concurrently with imaging or as a single field measurement per readout. The measured field fluctuations were then accounted for in the image reconstruction. RESULTS: Significant field fluctuations due to motion were observed in all subjects, resulting in severe artifacts in uncorrected images. The artifacts were largely removed by reconstruction based on field monitoring. Accounting for field perturbations up to the 1st spatial order was generally sufficient to recover good image quality. CONCLUSIONS: It has been demonstrated that artifacts due to physiologically induced dynamic field perturbations can be greatly reduced by retrospective image correction based on field monitoring. The necessity to perform such correction is greatest at high fields and for field-sensitive techniques such as T2*-weighted imaging.

Original publication

DOI

10.1002/mrm.25303

Type

Journal article

Journal

Magn Reson Med

Publication Date

05/2015

Volume

73

Pages

1833 - 1843

Keywords

T2*-weighted imaging, concurrent field monitoring, field fluctuations, magnetic field monitoring, physiological noise, Adult, Artifacts, Brain, Female, Humans, Image Enhancement, Image Interpretation, Computer-Assisted, Magnetic Resonance Imaging, Magnetic Resonance Imaging, Cine, Magnetic Resonance Spectroscopy, Male