Frequency difference mapping applied to the corpus callosum at 7T

Tendler, Benjamin C.; Bowtell, Richard

Abstract

Purpose: Frequency difference mapping (FDM) is a phase processing technique which characterises the non-linear temporal evolution of the phase of gradient echo signals. Here, a novel FDM processing algorithm is introduced, which is shown to reveal information about white matter microstructure. Unlike some other phase processing techniques, the FDM algorithm presented here does not require the use of phase unwrapping or sophisticated image processing. It uses a series of scaled complex divisions to unwrap phase and remove background fields.

Methods: 10 healthy subjects underwent a series of single-slice, sagittal multi-echo gradient echo scans at 7T with the slice positioned at the mid-line. Phase data were processed with the novel FDM algorithm and the temporal evolution of the magnitude signal and frequency difference was examined in 5 regions of the corpus callosum (genu, anterior body, middle body, posterior body and splenium).

Results: Consistent frequency difference contrast relative to surrounding tissue was observed in all subjects in the corpus callosum, and in other white matter regions where the nerves fibres run perpendicular to 𝐵0, such as the superior cerebellar peduncle. Examination of the frequency difference curves shows distinct variations over the corpus callosum, with the genu and splenium displaying larger frequency differences than the other regions (in addition to a faster decay of the signal magnitude).

Conclusion: The novel FDM algorithm presented here yields images sensitive to tissue microstructure and microstructural differences over the corpus callosum in a simple manner, without the requirement for phase unwrapping or sophisticated image processing.

Citation

Tendler, B. C., & Bowtell, R. (2019). Frequency difference mapping applied to the corpus callosum at 7T. Magnetic Resonance in Medicine, 81(5), 3017-3031. https://doi.org/10.1002/mrm.27626

• Journal Article Type: Article
• Acceptance Date: Nov 14, 2018
• Online Publication Date: Dec 23, 2018
• Publication Date: 2019-05
• Deposit Date: Nov 16, 2018
• Publicly Available Date: Dec 23, 2018
• Journal: Magnetic Resonance in Medicine
• Print ISSN: 0740-3194
• Electronic ISSN: 1522-2594
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 81
• Issue: 5
• Pages: 3017-3031
• DOI: https://doi.org/10.1002/mrm.27626
• Keywords: Radiology Nuclear Medicine and imaging
• Public URL: https://nottingham-repository.worktribe.com/output/1270892
• Publisher URL: https://onlinelibrary.wiley.com/doi/full/10.1002/mrm.27626