Multiplexer for selection of an mri compatible band stop filter or switch placed in series with a particular therapy electrode of an active implantable medical device

Abstract

An MRI-compatible electronic medical therapy system includes an active medical device connected to a plurality of electrodes. A multiplexer circuit includes at least one circuit protection device in electrical series with the electrodes and the medical device. The circuit protection device can be in the form of a switch or a band stop filter. The circuit protection device is adapted to permit current flow therethrough during normal medical device related therapy, but substantially prevent current flow therethrough in the presence of an induced electromagnetic field.

1 . An MRI-compatible electronic medical therapy system, comprising:
 an active medical device (AMD) having an electronic circuit and a power supply;   a plurality of electrodes electrically connected to the electronic circuit of the AMD and adapted for insertion into or connection with biological tissue; and   a multiplexer circuit, including at least one, but fewer than the plurality of electrodes, circuit protection device in electrical series with the plurality of electrodes and the AMD electronic circuit, the at least one circuit protection device adapted to permit current flow therethrough during normal AMD-related therapy, but substantially prevent current flow therethrough in the presence of an induced electromagnetic field.   
   
   
       2 . The system of  claim 1 , wherein the electromagnetic field comprises a radio frequency, magnetic or static field. 
   
   
       3 . The system of  claim 1 , wherein the electromagnetic field comprises an MRI field. 
   
   
       4 . The system of  claim 1 , wherein the circuit protection device comprises a switch. 
   
   
       5 . The system of  claim 4 , wherein the switch is closed during normal AMD-related therapy, but opens in the presence of the electromagnetic field. 
   
   
       6 . The system of  claim 5 , wherein the switch comprises a Micro-Electromechanical System (MEMS) switch. 
   
   
       7 . The system of  claim 6 , wherein the MEMS switch includes a micro-static relay activated in the presence of an electrostatic field. 
   
   
       8 . The system of  claim 6 , wherein the MEMS switch includes a micro-magnetic relay activated in the presence of an magnetic field. 
   
   
       9 . The system of  claim 1 , wherein the switch comprises a switch assembly having multiple switches or switch relays. 
   
   
       10 . The system of  claim 1 , wherein the circuit protection device comprises a band stop filter. 
   
   
       11 . The system of  claim 10 , wherein the band stop filter comprises a capacitor in parallel with a resistor, the levels of capacitance and resistance selected for a predetermined frequency range of the electromagnetic field. 
   
   
       12 . An MRI-compatible electronic medical therapy system, comprising:
 an active medical device (AMD) having an electronic circuit and a power supply;   a plurality of electrodes electrically connected to the electronic circuit of the AMD and adapted for insertion into or connection with biological tissue; and   a multiplexer circuit, including at least one, but fewer than the plurality of electrodes, switch in electrical series with the plurality of electrodes and the AMD electronic circuit, the at least one switch normally closed to permit current flow therethrough during normal AMD-related therapy, but open to prevent current flow therethrough in the presence of an induced radio frequency, magnetic or static electromagnetic field.   
   
   
       13 . The system of  claim 12 , wherein the electromagnetic field comprises an MRI field. 
   
   
       14 . The system of  claim 12 , wherein the switch comprises a Micro-Electromechanical System (MEMS) switch. 
   
   
       15 . The system of  claim 14 , wherein the MEMS switch includes a micro-static relay activated in the presence of an electrostatic field. 
   
   
       16 . The system of  claim 14 , wherein the MEMS switch includes a micro-magnetic relay activated in the presence of an magnetic field. 
   
   
       17 . The system of  claim 12 , wherein the switch comprises a switch assembly having multiple switches or switch relays. 
   
   
       18 . An MRI-compatible electronic medical therapy system, comprising:
 an active medical device (AMD) having an electronic circuit and a power supply;   a plurality of electrodes electrically connected to the electronic circuit of the AMD and adapted for insertion into or connection with biological tissue; and   a multiplexer circuit, including at least one, but fewer than the plurality of electrodes, band stop filter in electrical series with the plurality of electrodes and the AMD electronic circuit, the at least one band stop filter adapted to permit current flow therethrough during normal AMD-related therapy, but substantially prevent current flow therethrough in the presence of an induced radio frequency, magnetic or static electromagnetic field.   
   
   
       19 . The system of  claim 18 , wherein the electromagnetic field comprises an MRI field. 
   
   
       20 . The system of  claim 18 , wherein the at least one band stop filter comprises a capacitor in parallel with a resistor, the levels of capacitance and resistance selected for a predetermined frequency range of the electromagnetic field.