Simulations of high permittivity materials for 7 T neuroimaging and evaluation of a new barium titanate-based dielectric.
Magn Reson Med
; 67(4): 912-8, 2012 Apr.
Article
em En
| MEDLINE
| ID: mdl-22287360
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 â¼90. Significant improvements are found for values between 90 and â¼180. If the relative permittivity is increased above â¼180 then areas of very low transmit efficiency are produced. For a 1-cm thick pad, the corresponding numbers are â¼60 and â¼120, respectively. Based upon the findings, a new material (barium titanate, relative permittivity â¼150) is used to produce thin (â¼5 mm) dielectric pads which can easily be placed within a standard receive head array. Experimental measurements of transmit sensitivities, as well as acquisition of T(2) - and T 2*-weighted images show the promise of this approach.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Titânio
/
Mapeamento Encefálico
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Imageamento por Ressonância Magnética
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Compostos de Bário
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Neuroimagem
Tipo de estudo:
Prognostic_studies
Limite:
Humans
Idioma:
En
Ano de publicação:
2012
Tipo de documento:
Article