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Approaching Ultimate Intrinsic SNR in a Uniform Spherical Sample with Finite Arrays of Loop Coils.

Author information

1
Center for Advanced Imaging Innovation and Research (CAI R) and Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY ; The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, NY ; NYU WIRELESS, Polytechnic Institute of New York University, Brooklyn, NY.

Abstract

We investigated to what degree and at what rate the ultimate intrinsic (UI) signal-to-noise ratio (SNR) may be approached using finite radiofrequency detector arrays. We used full-wave electromagnetic field simulations based on dyadic Green's functions to compare the SNR of arrays of loops surrounding a uniform sphere with the ultimate intrinsic SNR (UISNR), for increasing numbers of elements over a range of magnetic field strengths, voxel positions, sphere sizes, and acceleration factors. We evaluated the effect of coil conductor losses and the performance of a variety of distinct geometrical arrangements such as "helmet" and "open-pole" configurations in multiple imaging planes. Our results indicate that UISNR at the center is rapidly approached with encircling arrays and performance is substantially lower near the surface, where a quadrature detection configuration tailored to voxel position is optimal. Coil noise is negligible at high field, where sample noise dominates. Central SNR for practical array configurations such as the helmet is similar to that of close-packed arrangements. The observed trends can provide physical insights to improve coil design.

KEYWORDS:

dyadic green’s function; magnetic resonance imaging; parallel imaging; radiofrequency coil performance; signal-to-noise ratio; ultimate intrinsic signal-to-noise ratio

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