A wireless magnetic resonance imaging (MRI) scanner bore tube assembly has a radio frequency (RF) antenna, a microwave antenna array and an electrical screen. The RF antenna is formed of a series of RF antenna elements, each comprising a rung. The rungs are spaced at intervals of substantially half of the wavelength of the frequency of operation of the microwave antenna array. The microwave antenna array is formed by a series of microwave antenna elements interleaved between the rungs and the screen acts as a reflector to reflect signals from the microwave antenna elements towards the centre of the bore tube.