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 (NM) receiver coil. A fiberoptic cable extending the length of the interventional device is used In conjunction with an externa l light source to deliver light to the photoresistor. Exposing the photores istor to light changes its bulk resistance and greatly lowers the Q of the parallel resonant circuit, effectively detuning it. By combining this optic al detuning scheme with inductive coupling of the interventional device-mou nted microcoils, to a standard MRI coil, a completely wireless device for a ctive device tracking has been created. This new device improves on current technology by simplifying device complexity and reducing patient risk by e liminating the need for electrical connections between the device-mounted m icrocoils to the MR receiver channel. J. Magn. Reson. Imaging 2000; 12:632- 638. (C) 2000 Wiley-Liss, Inc.