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Comparision of new element designs for combined RF-Shim arrays at 7 T.
Winkler, Simone A; Warr, Paul A; Stockmann, Jason P; Mareyam, Azma; Keil, Boris; Watkins, Ronald D; Wald, Lawrence L; Rutt, Brian K.
Afiliação
  • Winkler SA; Department of Radiology, Stanford University, Stanford, California, USA., Grant sponsor: NIH K99 EB24341., Grant sponsor: NIH P41 EB015891., Grant sponsor: NSERC., Grant sponsor: BWF.
  • Warr PA; Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA.
  • Stockmann JP; Department of Electrical and Electronic Engineering, University of Bristol, UK.
  • Mareyam A; Department of Electrical and Electronic Engineering, University of Bristol, UK.
  • Keil B; Technische Hochschule Mittelhessen, Germany.
  • Watkins RD; Department of Radiology, Stanford University, Stanford, California, USA., Grant sponsor: NIH K99 EB24341., Grant sponsor: NIH P41 EB015891., Grant sponsor: NSERC., Grant sponsor: BWF.
  • Wald LL; Department of Electrical and Electronic Engineering, University of Bristol, UK.
  • Rutt BK; Department of Radiology, Stanford University, Stanford, California, USA., Grant sponsor: NIH K99 EB24341., Grant sponsor: NIH P41 EB015891., Grant sponsor: NSERC., Grant sponsor: BWF.
Article em En | MEDLINE | ID: mdl-30613196
ABSTRACT

PURPOSE:

To identify novel concepts for RF-shim loop architectures suitable for 7T made of two concentric conducting loops fulfilling RF and DC functions, respectively, and to determine their relative SNR performance. The goal is to minimize interference between the two systems while making efficient use of the space closest to the body. THEORY We show by means of theoretical derivation of the frequency spectrum that the proposed two-loop structure exhibits an anti-resonant null and a resonant peak in the frequency domain.

METHODS:

The proposed structure is comprised of two concentric wire loops either arranged as nested loops or in the form of a coaxial cable, in which the two conductors carry the RF and shim signals, respectively. We use theory, simulation, and phantom measurements to obtain frequency spectra and SNR maps for the proposed structures.

RESULTS:

Retained SNR is found to be 75% in the coaxial loop and ranges from 57% to 67% in three different coaxial configurations. We have found both implementations to be a viable concept for the use in RF-shim devices if remaining SNR limitations can be overcome.

CONCLUSIONS:

We have investigated two new design modalities in 7T RF-shim coil design that separate the RF and shim conductors such that the previously proposed toroidal chokes are eliminated - thereby removing undesired additional loss, bulk, and design complexity.
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Texto completo: 1 Base de dados: MEDLINE Idioma: En Ano de publicação: 2018 Tipo de documento: Article

Texto completo: 1 Base de dados: MEDLINE Idioma: En Ano de publicação: 2018 Tipo de documento: Article