A catheter-based RF receiver for internal magnetic resonance imaging is described. The device consists of a double-sided thin-film circuit, mounted on a hollow catheter. The system was originally designed for biliary ductal imaging, but is also potentially useful for vascular imaging. Signals are detected using a resonant L-C circuit at the catheter tip, transmitted along the catheter using an array of coupled L-C resonators, and coupled into a conventional RF system using a demountable inductive transducer. Protection against external B1 and E fields is obtained by using figure-of-eight-shaped elements with an electrical length shorter than that of an immersed half-wave dipole. Electromagnetic modeling software (AWR Microwave Office) is used to analyze a system designed for 1 H imaging at 1.5T, determine the effect of the tissue surround, demonstrate signal detection and transmission and verify intrinsic safety.