Sci. Adv. Today 2 (2016) 25249  
  Research Article  
   
   
         
Determination of the dielectric constant for passive RF shimming at high field  
  Mohan Jayatilakea, Judd Storrsa, Wenjang Chua,c, Jing-Huei Leea,b,c  
     
a Center for Imaging Research, University of Cincinnati, Cincinnati, OH, United States
b Biomedical Engineering, University of Cincinnati, Cincinnati, OH, United States
c Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, OH, United States

   
  Abstract  
  One of the requirements for an optimal Magnetic Resonance Imaging (MRI) at high fields needs a homogeneous RF (B1) field; however, dielectric properties of water in the human brain cause B1 field inhomogeneities and signal loss in the periphery of the brain images. These result from constructive and destructive RF interactions of complex wave behaviour, which become worse with increasing Larmor frequency. Placement of a shim object with high dielectric constant adjacent to the body has been proposed as a method for reducing B1 inhomogeneity by altering wave propagation within the volume of interest. Selecting the appropriate permittivity and the quantity of shim material is essential. While previous work has determined the dielectric properties of the shim object empirically, this work introduces an improved theoretical framework for determining the requisite dielectric constant of the passive shim material directly and verifies the accuracy using the simulation field maps.  
     
   
  Cite this article as:  
  Mohan Jayatilake, Judd Storrs, Wenjang Chu, Jing-Huei Lee, Determination of the dielectric constant for passive RF shimming at high field , Sci. Adv. Today 2 (2016) 25249.