A layer model for RF penetration, heating, and screening in NMR

A solvable layer model is presented for the problem of a conducting, dielectric object in the presence of an external RF magnetic field. The corresponding structure permits exact analytic solutions for currents, fields, and image response. This provides a testing ground for certain transmission and receiving issues in magnetic resonance imaging, including RF power deposition, high-frequency screening, and other wavelength effects. Free-space wavelength effects can be accounted for exactly in this solution. A successful comparison with phantom measurements indicates that the model is an adequate guide of what to expect for more realistic geometries at high frequencies and can be extended to mimic actual body layers. The general results exhibit less penetration and heating effects than expected. The layer model is useful for demonstrating the in vivo extraction of electrical tissue properties and for tests and comparisons of various numerical methods.