A magnetic resonance imaging (MRI) duodenoscope is demonstrated, by combining non-magnetic endoscope components with a thin-film receiver based on a magneto-inductive waveguide. The waveguide elements consist of figure-of-eight shaped inductors formed on either side of a flexible substrate and parallel plate capacitors that use the substrate as a dielectric. Operation is simulated using equivalent circuit models and by computation of two- and three-dimensional sensitivity patterns. Circuits are fabricated for operation at 127.7 MHz by double-sided patterning of copper-clad Kapton and assembled onto non-magnetic flexible endoscope insertion tubes. Operation is verified by bench testing and by 1H MRI at 3T using phantoms. The receiver can form a segmented coaxial image along the length of the endoscope, even when bent, and shows a signal-to-noise-ratio advantage over a surface array coil up to three times the tube diameter at the tip. Initial immersion imaging experiments have been carried out and confirm an encouraging lack of sensitivity to RF heating.
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