MRI QD RF coil having diode switched detuning circuit producing reduced artifact

A detuning/decoupling arrangement for a Magnetic Resonance Imaging (MRI) system quadrature RF coil arrangement (of the typing using the nuclear magnetic resonance, or NMR, phenomenon) uses switching diodes to selectively connect and disconnect portions of a segmented RF coil in response to a DC control signal. The DC control signal selectively forward biases and reverse biases the switching diodes. The DC control current flows through the RF coil itself, through the diodes, and then through the center conductor of a semi-rigid transmission line disposed in proximity to the RF coil. Because the DC current flowing through the transmission line is equal and opposite to the DC current flowing through the RF coil, the net magnetic field generated by the DC current flow is approximately zero -- eliminating artifacts in the MRI image that would otherwise be generated due to continuous DC current flowing whenever the coil is being used to transmit or receive RF.