An insertable intracavity probe for use in magnetic resonance imaging of an area of interest in a body cavity particularly the colon, has an elongate shaft with a handle at its proximal end and an inflatable balloon structure at its distal end. The balloon structure has an outer balloon containing a loop-type pickup coil for connection to an interfacing network. The coil is sandwiched between two internal separately inflatable balloons, and when the probe is inserted, the coil can be optimally positioned relative to the area of interest by controlled differential inflation of the balloons. The probe also has an insertable rod-like mandrel for providing twisting orbital-type movement of the balloon structure on the shaft, by rotation of the mandrel, useful to steer the probe along curves or bends in the body cavity when it is being inserted. In a modified form of the probe, the mandrel can be used to rotate the coil and the internal balloons as a unit within the outer balloon for optimal in situ angular positioning of the coil.