Implantable Tissue Ischemia Sensor

Abstract

An implantable ischemia detection system in which a white LED ( 105 ) produces a continuous, visible, broadband light illuminating a target site ( 125 ). Light backscattered by the target is collected by a sensor ( 155 ), allowing for an index of ischemia to be determined, and subsequently transmitted by a sending unit ( 167 ). Power is provided by an internal power source ( 179 ). The entire implantable device is encapsulated by a biocompatible shell ( 102 ) to add long-term safety with regard to implantation.

1 . An implantable device for invasive implantation internally comprising:
 a light source for illuminating a target with light;   a sensor configured so as to detect light backscattered from local capillary and extravascular tissue within the target site onto said sensor and to provide a tissue oxygenation output signal that is a direct function of the presence or degree of internal tissue ischemia based at least on said light backscattered from said site;   a power source configured to supply energy to said sensor and said light source; and   an exterior shell enclosing said power source, light source, and sensor configured so as to be biocompatible with respect to implantation internally.   
     
     
         2 . A method of monitoring or detecting local tissue ischemia internally in a living tissue comprising the steps of:
 (a) invasively implanting internally a device having a light emitter and a light detector;   (b) illuminating an internal target site with light from the light emitter;   (c) detecting light returning from tissue using the light detector, said returning light substantially reflecting capillary and extravascular tissue sites; and   (d) determining a measure that is a function of local tissue ischemia internally based upon the detected light, said detected light substantially reflecting said capillary and extravascular tissue internally at the local target site.   
     
     
         3 . A device for implantation internally comprising:
 (a) a white LED for illuminating a target site with light;   (b) a wavelength-resolved linear CCD configured so as to detect light substantially reflecting light backscattered from local capillary and extravascular tissue within the target site onto said CCD;   (c) a sensor configured so as to determine, based at least upon said reflected light detected by said sensor, an output signal that is a function of the presence or degree of local tissue ischemia internally;   (d) a transmitter for receiving and transmitting said output signal;   (e) a an inductive coil for receiving power configured to supply energy to said LED, said CCD, and said transmitter; and   (f) an exterior shell configured so as to be biocompatible with respect to implantation internally, said shell housing one or more said LED, CCD, sensor, transmitter and inductive coil.   
     
     
         4 . The method of  claim 2 , further including the step of transmitting data before or after said determined measure is determined.