An optical system for wireless detuning of parallel resonant circuits

A new optical method of detuning parallel resonant circuits is described. T his method involves the integration of a photoresistor in parallel with the inductor and capacitor of a parallel resonant circuit, in this case a magn etic resonance imaging (MRI) receiver coil. A fiberoptic, cable extending t he length of the interventional device is used in conjunction with an exter nal light source to deliver light to the photoresistor. Exposing the photor esistor to light changes its bulk resistance and greatly lowers the Q of th e parallel resonant circuit, effectively detuning it. By combining this opt ical detuning scheme with inductive coupling of the interventional device-m ounted microcoils to a standard PARI coil, a completely wireless device for active device tracking has been created. This new device improves on curre nt technology by simplifying device. complexity and reducing patient risk b y eliminating the need for electrical connections between the device-mounte d microcoils to the AIR receiver channel. (C) 2000 Wiley-Liss, Inc.