Simulations of high permittivity materials for 7 T neuroimaging and evaluation of a new barium titanate‐based dielectric
Open Access
- 27 January 2012
- journal article
- research article
- Published by Wiley in Magnetic Resonance in Medicine
- Vol. 67 (4), 912-918
- https://doi.org/10.1002/mrm.24176
Abstract
High permittivity “dielectric pads” have been shown to increase image quality at high magnetic fields in regions of low radiofrequency transmit efficiency. This article presents a series of electromagnetic simulations to determine the effects of pad size and geometry, relative permittivity value, as well as thickness on the transmit radiofrequency fields for neuroimaging at 7 T. For a 5-mm thick pad, there is virtually no effect on the transmit field for relative permittivity values lower than ∼90. Significant improvements are found for values between 90 and ∼180. If the relative permittivity is increased above ∼180 then areas of very low transmit efficiency are produced. For a 1-cm thick pad, the corresponding numbers are ∼60 and ∼120, respectively. Based upon the findings, a new material (barium titanate, relative permittivity ∼150) is used to produce thin (∼5 mm) dielectric pads which can easily be placed within a standard receive head array. Experimental measurements of transmit sensitivities, as well as acquisition of T2- and T-weighted images show the promise of this approach. Magn Reson Med, 2012.Keywords
This publication has 16 references indexed in Scilit:
- Dielectric materials in magnetic resonanceConcepts in Magnetic Resonance Part A, 2011
- Improvements in high‐field localized MRS of the medial temporal lobe in humans using new deformable high‐dielectric materialsNMR in Biomedicine, 2010
- Reducing SAR and enhancing cerebral signal‐to‐noise ratio with high permittivity padding at 3 TMagnetic Resonance in Medicine, 2010
- The Virtual Family—development of surface-based anatomical models of two adults and two children for dosimetric simulationsPhysics in Medicine & Biology, 2009
- Improvement in B1-inhomogeneity artifacts in the abdomen at 3T MR imaging using a radiofrequency cushionJournal of Magnetic Resonance Imaging, 2008
- MR imaging of the female pelvis at 3 Tesla: Evaluation of image homogeneity using different dielectric padsJournal of Magnetic Resonance Imaging, 2007
- Actual flip‐angle imaging in the pulsed steady state: A method for rapid three‐dimensional mapping of the transmitted radiofrequency fieldMagnetic Resonance in Medicine, 2006
- Imaging artifacts at 3.0TJournal of Magnetic Resonance Imaging, 2006
- Manipulation of image intensity distribution at 7.0 T: Passive RF shimming and focusing with dielectric materialsJournal of Magnetic Resonance Imaging, 2006
- Standing-wave and RF penetration artifacts caused by elliptic geometry: an electrodynamic analysis of MRIIEEE Transactions on Medical Imaging, 1998