| 摘要 |
A surface structure with preselected magnetic permeability in the plane of the surface comprises an array of elements consisting of multi-turn helical loops made for example by tracks 10, 11 on a printed circuit board plated through for example by vias 13 and with the possible addition of a parallel capacitance 14, the pitch of the array being much less than the wavelength of the electromagnetic radiation to which the surface exhibits predetermined values of magnetic permeability, which can range from negative values such as -1 to 0 and to positive values greater than 1. The latter act as a duct for magnetic flux allowing receive coils and magnetic resonance imaging apparatus to be spaced from the surface of a patient and also to allow for screening purposes within magnetic resonance imaging apparatus. A value of magnetic permeability of-1 enables the surface structure to be used as a reflecting surface.
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