Effect of an annular sleeve of high permittivity material on resonant modes and homogeneity of a birdcage coil

Abstract

Fig. 1 Simulation set-up. High pass head-sized birdcage with a dielectric (blue) sleeve (A, B) or brick (C) with dimensions 3.5 cm x 8.5 cm x 26 cm. ABSTRACTWe investigated how high permittivity materials affect the S-parameters and transmit efficiency of a head-sized birdcage coil. We also studied whether re-tuning and matching are necessary for improved performance. While adjusting the S-parameters is possible during coil development and for prototype coils, it is often unfeasible to re-tune and match commercially manufactured coils, and poses a challenge after adding dielectric material to such coils. Our work demonstrates the change in the S-parameters and the transmit efficiency after placing a dielectric sleeve within a head-sized birdcage coil, and reports that coil performance can be improved after re-tuning and matching the coil in the presence of the dielectric material.

Improved image quality and reduced power deposition in the spine at 3 T using extremely high permittivity materials

“…In previous studies, dielectric pads with a relative permittivity of ∼300 have been shown to increase the transmit efficiency and reduce the specific absorption rate (SAR) in cardiac , abdominal , and cervical spine applications at 3T. In the current work, materials developed by the Penn State group with relative permittivity values more than three times greater than those used in previous body imaging studies are investigated. The effect of these materials on the transmit RF field, receive sensitivity, and overall diagnostic quality of the images has been analyzed.…”