A 31-channel Integrated "AC/DC" B Shim and Radiofrequency Receive Array Coil for Improved 7T MRI

Overview

Journal Magn Reson Med

Publisher Wiley

Specialty Radiology

Date 2021 Oct 11

PMID 34632626

Citations 11

Authors

Jason P Stockmann

Nicolas S Arango

Thomas Witzel

Azma Mareyam

Charlotte Sappo

Jiazheng Zhou

Lucas Jenkins

Lincoln Craven-Brightman

Eugene Milshteyn

Mathias Davids

W Scott Hoge

Monika Sliwiak

Shahin Nasr

Boris Keil

Elfar Adalsteinsson

Bastien Guerin

Jacob K White

Kawin Setsompop

Jonathan R Polimeni

Lawrence L Wald

Affiliations

Soon will be listed here.

Abstract

Purpose: To test an integrated "AC/DC" array approach at 7T, where B inhomogeneity poses an obstacle for functional imaging, diffusion-weighted MRI, MR spectroscopy, and other applications.

Methods: A close-fitting 7T 31-channel (31-ch) brain array was constructed and tested using combined Rx and ΔB shim channels driven by a set of rapidly switchable current amplifiers. The coil was compared to a shape-matched 31-ch reference receive-only array for RF safety, signal-to-noise ratio (SNR), and inter-element noise correlation. We characterize the coil array's ability to provide global and dynamic (slice-optimized) shimming using ΔB field maps and echo planar imaging (EPI) acquisitions.

Results: The SNR and average noise correlation were similar to the 31-ch reference array. Global and slice-optimized shimming provide 11% and 40% improvements respectively compared to baseline second-order spherical harmonic shimming. Birdcage transmit coil efficiency was similar for the reference and AC/DC array setups.

Conclusion: Adding ΔB shim capability to a 31-ch 7T receive array can significantly boost 7T brain B homogeneity without sacrificing the array's rdiofrequency performance, potentially improving ultra-high field neuroimaging applications that are vulnerable to off-resonance effects.

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