TBME presents

A Novel Method to Decrease Electric Field and SAR using an External High Dielectric Sleeve at 3T Head MRI: Numerical and Experimental Results

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Bu S. Park, Sunder S. Rajan, Joshua W. Guag, and Leonardo M. Angelone, Division of Physics (DP)/OSEL/CDRH, Food and Drug Administration (FDA), USA, Volume 62, Issue 4, Page: 1063-1069

TBME-00935-2014_Figure 2

Materials with high dielectric constant (HDC) have been used in high field MRI to decrease specific absorption rate (SAR), increase magnetic field intensity, and increase signal-to-noise ratio (SNR). In previous studies, the HDC materials were placed inside the RF coil decreasing the space available. This study describes an alternative approach that considers an HDC-based sleeve placed outside the RF coil. The effects of a HDC on the electromagnetic (EM) field were studied using numerical simulations with a coil unloaded and loaded with a human head model. In addition, experimental EM measurements at 128 MHz were performed inside a custom-made head coil, fitted with a distilled water sleeve. The numerical simulations showed up to 40% decrease in maximum 10g-avg. SAR on the surface of the head model with a HDC material of Barium Titanate. Experimental measurements also showed up to 20% decrease of maximum electric field using a HDC material of distilled water. The proposed method can be incorporated in the design of high field transmit RF coils.

Index Terms — Barium Titanate, distilled water, SAR, birdcage coil, FDTD, coil design

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