A wireless patient sensor (16) for monitoring a patient (14) during an MRI examination, the patient sensor comprising: a housing positionable near the patient (14) during the MRI examination an input circuit for receiving a physiological signal (22) from the patient (14) a transmitter (30) for transmitting the physiological signal (19) wirelessly to an external station (24) in a manner compatible with operation of the MRI machine and a power source contained in the housing and providing power for the input circuit and transmitter (30), the power source comprising a capacitor storage (36) without chemical batteries. A system of powering of a wireless patient monitor using capacitors is also provided.