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 language | English (US) |
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Pages (from-to) | 2122-2138 |
Number of pages | 17 |
Journal | Magnetic resonance in medicine |
Volume | 80 |
Issue number | 5 |
DOIs | |
State | Published - Nov 2018 |
Externally published | Yes |
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