Premium
Improved automatic off‐resonance correction without a field map in spiral imaging
Author(s) -
Man LaiChee,
Pauly John M.,
Macovski Albert
Publication year - 1997
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910370616
Subject(s) - a priori and a posteriori , spiral (railway) , imaging phantom , artifact (error) , field (mathematics) , computer science , algorithm , artificial intelligence , resonance (particle physics) , field of view , computer vision , mathematics , physics , optics , mathematical analysis , philosophy , epistemology , particle physics , pure mathematics
Abstract Non‐2DFT k ‐space readout strategies are useful in fast imaging but prone to blurring when reconstructed off resonance. Field inhomogeneities or susceptibility variations, coupled with a long readout time, are the major sources of this artifact. Correction methods based on a priori off‐resonance information such as an acquired field map have been proposed in the literature. An alternative approach estimates the spatially varying off‐resonance frequency from the data itself before applying a correction. In this latter approach there is a tradeoff between the extent of correction and the chance of increased artifact due to estimation error. This paper introduces an improved algorithm for field map estimation which is both faster and more robust than the existing method. It uses a multi‐stage estimation of the field map, starting from a coarse estimate both in frequency and space and proceeds towards higher resolution. The new algorithm is applied to phantom and in vivo images acquired with radial and spiral sequences to give sharper images.