Optical control of radio frequency antennae in a magnetic resonance imaging system

An antenna assembly for receiving a magnetic resonance signals from substance, said antenna assembly comprising:

• a radio frequency receive antenna in which the magnetic resonance signals induce an electric current, the radio frequency receive antenna having first and second terminals;
• first and second capacitors connected in series with the radio frequency receive antenna to form a resonant circuit which resonates at a Larmor frequency of the substance;
• a node between the first and second capacitors;
• a reactive electrical device having a first terminal connected to the node and having a second terminal;
• a photosensitive first semiconductor switch connected between the second terminal of the reactive electrical device and the first terminal of the radio frequency receive antenna;
• and
• a receive coil control operatively coupled to illuminate the photosensitive first semiconductor switch and render the photosensitive first semiconductor switch in a conductive state causing response of the resonant circuit at the Larmor frequency to be substantially nulled.

A controlled antenna assembly for a magnetic resonance imaging system that produces images of a substance and prevents electrical shock hazards, said antenna assembly comprising:

• a resonant circuit having a first inductance and being tuned to resonate at a Larmor frequency of the substance;
• a reactive electrical device;
• a photosensitive first semiconductor switch selectively connecting the reactive electrical device to the resonant circuit, wherein impingement of light on the photosensitive first semiconductor switch alters connection of the reactive electrical device to the resonant circuit thereby substantially nulling response of said resonant circuit at the Larmor frequency;
• and
• a receive coil control coupled to illuminate the photosensitive first semiconductor switch and said receive coil control being coupled to form a signal path to isolate hazardous electrical voltages and currents from said substance.