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Abstract #2339

Use of Opposed Shim Currents for Infold Reduction on a UHF MRI System with Head Gradient

Christopher John Wiggins1, Marion Caillat1, Denis Le Bihan1, Franz Schmitt2, Eva Eberlein2

1CEA/NeuroSpin, Gif-Sur-Yvette cedex, France; 2Siemens AG, Healthcare Sector Imaging & IT Division, Magnetic Resonance, Erlangen, Germany

The use of a head gradient set within a wholebody magnet can lead to significant artifacts. Signal arising from the shoulders is encoded in such a way that it aliases into the main image. Such artifacts are particularly pronounced at higher field, where B1 effects cause the sensitive region of volume coils to extend out into the chest and shoulder region. Previous approaches have tried to diminish the RF penetration in this area (through the use of RF shielding materials) or to disrupt the local field through using ferromagnetic material shown into a jacket that the subject wears. This study shows that with the use of both the wholebody and head gradient shim sets the signal from the shoulders could be dephased without affecting the signal from the head itself.