Bone and Joint Institute

Title

Inter-echo variance as a weighting factor for multi-channel combination in multi-echo acquisition for local frequency shift mapping

Document Type

Article

Publication Date

4-1-2015

Journal

Magnetic Resonance in Medicine

Volume

73

Issue

4

First Page

1654

Last Page

1661

URL with Digital Object Identifier

10.1002/mrm.25247

Abstract

© 2014 Wiley Periodicals, Inc. Purpose To develop and evaluate a local frequency shift (LFS) mapping method specifically designed for multi-echo acquisitions and multi-channel receive coils. Methods The proposed method uses the pixel-by-pixel inter-echo variance (IEV) as a weighting factor during channel-combination. Five healthy volunteers were scanned at 7 T. The IEV-weighted method was quantitatively compared to established (adaptive and Hermitian product) channel-combination methods with respect to IEV of LFS over the entire brain. Results In all experiments, the IEV-weighted method generated LFS maps free of artifacts caused by unwrapping errors. Based on measurements of the inter-echo frequency variance throughout the whole brain, the IEV-weighted method produced the lowest variation and the best contrast at the edge of the brain. Conclusion The primary finding of the present study is that accurate LFS maps are achievable if the data from each channel is processed independently prior to combination followed by a weighted combination using IEV as the weighting term. The software is freely available to the scientific community.

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