Abstract: An adjustable holder for a magnetic resonance imaging RF surface coil for imaging a part of the body such as the temporomandibular joint. Elements are provided for positioning and securing the RF surface coil at a first predetermined point along a longitudinal axis of the holder and for positioning and securing the RF surface coil at a second predetermined point transverse to the longitudinal axis and at a radial distance R from the longitudinal axis. The preferred embodiment provides orbital movement of the surface coil about the longitudinal axis using a pair of U-shaped runner guides disposed substantially transverse to the longitudinal axis and adjustable clamps in cooperative engagement with the runner guides. The surface coil may be adjusted along a path transverse to the longitudinal axis by way of an adjustable shaft or arm which can be moved inwardly and outwardly, and the surface coil can be pivoted in a step-wise manner using a pivot head having a plurality of equally spaced detents.

Abstract: Frequency tuning and coupling capacitances in MRI RF receive coils are typically realized, at least in part, as reverse biased varactor diodes. During RF tuning of the transmit coil (i.e., so as to achieve resonance and matched impedance conditions), at least some if not all of the varactors associated with the receive coil are forward biased so as to simultaneously maximize detuning of the receive coil to resonant frequencies removed as far as possible from that of the transmitter coil being tuned while also then substantially reducing the Q of the receive coil.