A full-wavelength dipole RF coil element for 7T MRI with maximized longitudinal FOV and twpeak SAR distribution
Recently multi-channel RF coils based on several longitudinally oriented strip-line elements have been successfully applied in ultra-high field MRI. Among the different utilized strip-line approaches, the symmetrically fed dipole RF coil element initially presented in  which was terminated by two meander in [2, 3] seems to be one of the most promising candidates. This 25 cm long dipole element is slightly longer than half a wavelength (“λ/2-plus”) and is therefore not intrinsically eigen-resonant. In  the first homogeneous “from top to toe” MR image at 7 T has been scanned with the help of a whole-body coil array consisting of 16 of these meander elements. The authors took 28 successive overlapping scans, each with a longitudinal extend of approx. 25 cm. On the basis of this λ/2-plus-approach we developed a longitudinally extended coil element which exhibits a nearly full-wavelength resonant current distribution (“λ-minus”) with two distinct improvements – an RF field of view (FOV) that is maximized due to the longer extent and a lowered peak SAR10g due to a more appropriate two-peak electric field distribution.
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