FUGUE

FMRIB's Utility for Geometrically Unwarping EPIs

Overview
FUGUE (FMRIB's Utility for Geometrically Unwarping EPIs) performs unwarping of an EPI image based on fieldmap data in order to correct for the geometric distortion introduced by inhomogeneous B0 fields. This is principally used to improve the registration between the EPI and structural MR images. It comes with a wide range of regularisation methods to suppress the effect of noise in the fieldmaps.

FUGUE is now implemented within the standard FEAT pre-processing scheme and is available via the FEAT GUI.

Note that FUGUE does not correct for motion-B0 interactions within a time-series.

In addition, a phase unwrapping utility is also included, PRELUDE (Phase Region Expanding Labeller for Unwrapping Discrete Estimates) to enable fieldmaps to be generated from the phase difference between appropriate gradient-echo or spin-echo images.

Papers
Abstracts on the effect of regularisation of the fieldmaps using FUGUE was presented at HBM 2001 and HBM 2004 (see 2001 and 2004 posters - in ps format). A paper on PRELUDE is published in MRM; also see the associated technical report (PS/PDF/HTML) and slideshow.

Software
PRELUDE and FUGUE are available as part of the FMRIB Software Library.