A new RF transmit coil for foot and ankle imaging at 7T MRI

Publication date: January 2018
Source:Magnetic Resonance Imaging, Volume 45
Author(s): Tales Santini, Junghwan Kim, Sossena Wood, Narayanan Krishnamurthy, Nadim Farhat, Carlos Maciel, Shailesh Raval, Tiejun Zhao, Tamer Ibrahim
A four-channel Tic-Tac-Toe (TTT) transmit RF coil was designed and constructed for foot and ankle imaging at 7T MRI. Numerical simulations using an in-house developed FDTD package and experimental analyses using a homogenous phantom show an excellent agreement in terms of B1⁺ field distribution and s-parameters. Simulations performed on an anatomically detailed human lower leg model demonstrated an B1⁺ field distribution with a coefficient of variation (CV) of 23.9%/15.6%/28.8% and average B1⁺ of 0.33μT/0.56μT/0.43μT for 1W input power (i.e., 0.25W per channel) in the ankle/calcaneus/mid foot respectively. In-vivo B1⁺ mapping shows an average B1⁺ of 0.29μT over the entire foot/ankle. This newly developed RF coil also presents acceptable levels of average SAR (0.07W/kg for 10g per 1W of input power) and peak SAR (0.34W/kg for 10g per 1W of input power) over the whole lower leg. Preliminary in-vivo images in the foot/ankle were acquired using the T2-DESS MRI sequence.



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