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Poster — Thur Eve — 13: Quantifying specific absorption rate of shielded RF coils through electromagnetic simulations for 7‐T MRI
Author(s) -
Belliveau JG,
Gilbert KM,
AbouKhousa M,
Me RS
Publication year - 2012
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4740121
Subject(s) - shielded cable , electromagnetic shielding , specific absorption rate , shield , electromagnetic coil , radiofrequency coil , radio frequency , rf power amplifier , materials science , optics , acoustics , signal (programming language) , absorption (acoustics) , nuclear magnetic resonance , physics , computer science , electrical engineering , optoelectronics , antenna (radio) , engineering , telecommunications , geology , petrology , amplifier , cmos , composite material , programming language
Ultra‐high field MRI has many advantages such as increasing spatial resolution and exploiting contrast never before seen in‐vivo. This contrast has been shown to be beneficial for many applications such as monitoring early and late effect to radiation therapy and transient changes during disease to name a few. However, at higher field strengths the RF wave, needed to for transmitting and receiving signal, approaches that of the head. This leads to constructive and deconstructive interference and a non ‐uniform flip angle over the volume being imaged. A transmit or transceive RF surface coil arrays is currently a method of choice to overcome this problem; however, mutual inductance between elements poses a significant challenge for the designer. A method to decouple elements in such an array is by using circumferential shielding; however, the potential benefits and/or disadvantages have not been investigated. This abstract primarily focuses on understanding power deposition — measured through Specific Absorption Rate — in the sample using circumferentially shielded RF coils. Various geometries of circumferentially shielded coils are explored to determine the behaviour of shield width and its effect on required transmit power and power deposition to the sample. Our results indicate that there is an optimization on shield width depending on the imaging depth. Additionally, the circumferential shield focuses the field more than unshielded coils, meaning that slight SAR may even be lower for circumferential shielded RF coils in array.