RESEARCH ARTICLE


High-Field fMRI for Human Applications: An Overview of Spatial Resolution and Signal Specificity



Cheryl A Olman1, 2, Essa Yacoub*, 2
1 Department of Psychology, University of Minnesota
2 Center for Magnetic Resonance Research, University of Minnesota, USA


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© Olman and Yacoub; Licensee Bentham Open

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at 2021 6th St SE, Minneapolis, MN 55455, USA; Tel: 612-626-2001; Fax: 612-626-2004; E-mail: yaco0006@umn.edu


Abstract

In the last decade, dozens of 7 Tesla scanners have been purchased or installed around the world, while 3 Tesla systems have become a standard. This increased interest in higher field strengths is driven by a demonstrated advantage of high fields for available signal-to-noise ratio (SNR) in the magnetic resonance signal. Functional imaging studies have additional advantages of increases in both the contrast and the spatial specificity of the susceptibility based BOLD signal. One use of this resultant increase in the contrast to noise ratio (CNR) for functional MRI studies at high field is increased image resolution. However, there are many factors to consider in predicting exactly what kind of resolution gains might be made at high fields, and what the opportunity costs might be. The first part of this article discusses both hardware and image quality considerations for higher resolution functional imaging. The second part draws distinctions between image resolution, spatial specificity, and functional specificity of the fMRI signals that can be acquired at high fields, suggesting practical limitations for attainable resolutions of fMRI experiments at a given field, given the current state of the art in imaging techniques. Finally, practical resolution limitations and pulse sequence options for studies in human subjects are considered.

Keywords: High field, High resolution, BOLD, Functional imaging, Spatial specificity, 7T, 3T, Human, fMRI.