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Proceedings Paper

Retrospective correction of B0-field-induced geometric distortions in multislice echo planar images: a 3D solution
Author(s): Roderick W. McColl; Edward A. Coburn
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Paper Abstract

A method has been developed to utilize a 3D B0 fieldmap, with a multi-volume-of-interest segmentation map, to quantify and correct geometric distortions in echo-planar images. The purpose is to provide accurate co-registration of anatomical MRI to functional MRI time course sequences. A data structure capable of extracting and reporting the necessary information forms a central part of the solution. Images were obtained from a 1.5 Tesla scanner with an experimental y-gradient insert coil. Two 3D-gradient echo sequences supply the data needed to calculate the B0 map across the volume. Segmentation of the volume into brain/background produces the data needed for the phase unwrapping and volume(s) of interest generation, from which the global B0 variation map is obtained. Subsequent EPI acquisition yields the fMRI time- course information. Tests were carried out on a phantom and a human volunteer engaged in a motor task (finger-tapping). Strong distortions were measured, and subsequently corrected, particularly near the petrous bone/mastoid air cells and in the frontal and maxillary sinuses. Additionally, a strong eddy current resulting from the unshielded y-gradient was detected. The method facilitates geometric distortion correction through an imaging volume, containing multiple regions of interest within a slice, starting from a single starting point.

Paper Details

Date Published: 25 April 2000
PDF: 11 pages
Proc. SPIE 3977, Medical Imaging 2000: Physics of Medical Imaging, (25 April 2000); doi: 10.1117/12.384533
Show Author Affiliations
Roderick W. McColl, Univ. of Texas Southwestern Medical Ctr. (United States)
Edward A. Coburn, Lockheed Martin Tactical Aircraft Systems (United States)

Published in SPIE Proceedings Vol. 3977:
Medical Imaging 2000: Physics of Medical Imaging
James T. Dobbins III; John M. Boone, Editor(s)

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