The ultimate intrinsic signal-to-noise ratio of loop- and dipole-like current patterns in a realistic human head model

Andreas Pfrommer, Anke Henning

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Purpose: The ultimate intrinsic signal-to-noise ratio (UISNR) represents an upper bound for the achievable SNR of any receive coil. To reach this threshold a complete basis set of equivalent surface currents is required. This study systematically investigated to what extent either loop- or dipole-like current patterns are able to reach the UISNR threshold in a realistic human head model between 1.5 T and 11.7 T. Based on this analysis, we derived guidelines for coil designers to choose the best array element at a given field strength. Moreover, we present ideal current patterns yielding the UISNR in a realistic body model. Methods: We distributed generic current patterns on a cylindrical and helmet-shaped surface around a realistic human head model. We excited electromagnetic fields in the human head by using eigenfunctions of the spherical and cylindrical Helmholtz operator. The electromagnetic field problem was solved by a fast volume integral equation solver. Results: At 7 T and above, adding curl-free current patterns to divergence-free current patterns substantially increased the SNR in the human head (locally >20%). This was true for the helmet-shaped and the cylindrical surface. On the cylindrical surface, dipole-like current patterns had high SNR performance in central regions at ultra-high field strength. The UISNR increased superlinearly with B0 in most parts of the cerebrum but only sublinearly in the periphery of the human head. Conclusion: The combination of loop and dipole elements could enhance the SNR performance in the human head at ultra-high field strength.

Original languageEnglish (US)
Pages (from-to)2122-2138
Number of pages17
JournalMagnetic resonance in medicine
Volume80
Issue number5
DOIs
StatePublished - Nov 2018

Keywords

  • RF coils
  • dipole antenna
  • dyadic Green's functions
  • electromagnetic simulation
  • realistic body model
  • ultimate intrinsic SNR

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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