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Optimized quadrature surface coil designs

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Abstract

Background

Quadrature surface MRI/MRS detectors comprised of circular loop and figure-8 or butterfly-shaped coils offer improved signal-to-noise-ratios (SNR) compared to single surface coils, and reduced power and specific absorption rates (SAR) when used for MRI excitation. While the radius of the optimum loop coil for performing MRI at depth d in a sample is known, the optimum geometry for figure-8 and butterfly coils is not.

Materials and methods

The geometries of figure-8 and square butterfly detector coils that deliver the optimum SNR are determined numerically by the electromagnetic method of moments. Figure-8 and loop detectors are then combined to create SNR-optimized quadrature detectors whose theoretical and experimental SNR performance are compared with a novel quadrature detector comprised of a strip and a loop, and with two overlapped loops optimized for the same depth at 3 T. The quadrature detection efficiency and local SAR during transmission for the three quadrature configurations are analyzed and compared.

Results

The SNR-optimized figure-8 detector has loop radius r 8 ~ 0.6d, so r 8/r 0 ~ 1.3 in an optimized quadrature detector at 3 T. The optimized butterfly coil has side length ~ d and crossover angle of ≥50° at the center.

Conclusions

These new design rules for figure-8 and butterfly coils optimize their performance as linear and quadrature detectors.

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Authors and Affiliations

  1. Departments of Radiology and Electrical and Computer Engineering, Johns Hopkins University, Division of MR research, 601 N. Caroline Street, JHOC room 4243, Baltimore, MD, 21287, USA

    Ananda Kumar & Paul A. Bottomley

Authors
  1. Ananda Kumar
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  2. Paul A. Bottomley
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Corresponding author

Correspondence to Ananda Kumar.

Additional information

This work is supported by NIH grant R01 RR15396.

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Kumar, A., Bottomley, P.A. Optimized quadrature surface coil designs. Magn Reson Mater Phy 21, 41 (2008). https://doi.org/10.1007/s10334-007-0090-2

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  • DOI: https://doi.org/10.1007/s10334-007-0090-2

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