D Truhn1, F Kiessling, V Schulz. 1. Institute of Experimental Molecular Imaging, Pauwelsstrafle 20, 52074 Aachen and Philips Research Europe-Aachen, Weisshausstr. 2, 52066 Aachen, Germany. daniel.truhn@googlemail.com
Abstract
PURPOSE: Integration of positron emission tomography (PET) and magnetic resonance (MR) in a merged device requires shielding of the PET detector electronics. The authors demonstrate that a multiple shell setup exhibits advantages over a single shell shielding enclosure. METHODS: A spherical shell model is used to derive analytical results. Numerical computations of the electromagnetic fields with a commercial software package (FEKO) and experiments are used to confirm our findings. RESULTS: Replacing a single shell enclosure by a multilayer approach barely changes its behavior toward low frequency magnetic fields (MR gradient fields), while improving shielding at high frequencies (proton resonant frequency) by orders of magnitude. CONCLUSIONS: For a given required shielding factor at the proton resonant frequency, the eddy currents induced by the MR gradient fields may be reduced by employing a multiple shell setup.
PURPOSE: Integration of positron emission tomography (PET) and magnetic resonance (MR) in a merged device requires shielding of the PET detector electronics. The authors demonstrate that a multiple shell setup exhibits advantages over a single shell shielding enclosure. METHODS: A spherical shell model is used to derive analytical results. Numerical computations of the electromagnetic fields with a commercial software package (FEKO) and experiments are used to confirm our findings. RESULTS: Replacing a single shell enclosure by a multilayer approach barely changes its behavior toward low frequency magnetic fields (MR gradient fields), while improving shielding at high frequencies (proton resonant frequency) by orders of magnitude. CONCLUSIONS: For a given required shielding factor at the proton resonant frequency, the eddy currents induced by the MR gradient fields may be reduced by employing a multiple shell setup.
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