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Electromagnetic characterisation of MR RF coils using the transmission-line modelling method
P J Cassidy1, S Grieve, K Clarke
1British Heart Foundation Molecular Cardiology Group, Department of Biochemistry, University of Oxford, South Parks Road, OX1 3QU, Oxford, UK. cassidy@bioch.ox.ac.uk
Magma (New York, N.Y.)
|February 14, 2002
Summary
The Transmission-Line Modelling (TLM) method accurately characterizes radiofrequency (RF) coils and samples for magnetic resonance imaging (MRI). This approach enables precise RF coil design and ensures safety by calculating specific absorption rate (SAR) limits.
Area of Science:
- Electromagnetics
- Magnetic Resonance Imaging
Background:
- Accurate electromagnetic characterization of RF coils and samples is crucial for MRI.
- Existing methods may have limitations in comprehensive analysis and safety assessment.
Purpose of the Study:
- To apply the Transmission-Line Modelling (TLM) method for electromagnetic characterization of RF coils and samples in MRI.
- To develop equations for comprehensive characterization based on TLM simulations.
- To extend TLM for designing safe pulse sequences considering tissue SAR and coil component limits.
Main Methods:
- Theoretical and experimental verification of the TLM method using surface, Alderman-Grant, and birdcage coils at 7 T.
- Calculation of electromagnetic characteristics including frequency response, field generation, energy storage, and power loss.
- Determination of coil resonant modes, B1 field profiles, Q factor, pulse length, and lumped-element circuit parameters.
Main Results:
- TLM successfully determined key electromagnetic parameters for RF coils.
- Equations were derived for comprehensive coil and sample characterization from TLM simulations.
- The method was extended to design safe multi-nuclear pulse sequences within SAR and component limits.
Conclusions:
- The TLM method provides a robust framework for the electromagnetic characterization of MRI RF coils and samples.
- TLM simulations enable detailed analysis of coil performance and safety parameters.
- This approach facilitates the design of advanced and safe MRI pulse sequences.
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