Heating/sensing catheter apparatus for minimally invasive application

Abstract

Catheter apparatus comprises a coaxial cable having proximal and distal ends. The cable includes a hollow center conductor, an outer conductor and an electrically insulating layer between the conductors. An antenna is at the distal end of the cable, and a diplexer is connected to the cable, the diplexer including a transmit path for connecting the antenna to a transmitter which transmits first frequency signals and a receive path for connecting the antenna to a receiver which detects second frequency signals the diplexer isolating the signals on the two paths from one another. A transmission line connects the cable to the diplexer, the transmission line having a segment with a tubular inner conductor one end of which is connected to the center conductor and a second end of which is adapted for connection to a coolant source, the center and inner conductors forming a continuous coolant pathway.

What is claimed is: 
     
         1 . Catheter apparatus comprising
 an elongated flexible coaxial cable having proximal and distal ends, said cable including a hollow center conductor, an outer conductor and an electrically insulating layer in an annular space between said conductors;   an antenna at the distal end of the cable;   a diplexer including a transmit path for connecting the antenna to a transmitter which transmits signals of a first frequency and a receive path for connecting the antenna to a receiver which detects signals of a second frequency, said diplexer isolating the signals on the two paths from one another;   a transmission line connecting the cable to the diplexer, said transmission line including a segment with a tubular inner conductor one end of which is connected to the center conductor of the cable and a second end of which is adapted for connection to a coolant source, said center conductor and said inner conductor forming a continuous coolant pathway.   
     
     
         2 . The apparatus defined in  claim 1  wherein said receive path includes a first electrical filter. 
     
     
         3 . The apparatus defined in  claim 1  and further including an impedance-matching transformer in series with the cable and the transmission line. 
     
     
         4 . The apparatus defined in  claim 1  wherein the cable outer conductor comprises braided conductive strands. 
     
     
         5 . The apparatus defined in  claim 1  wherein the cable insulating layer comprises a flexible winding of one or more dielectric strands having multiple fluid flow paths therebetween. 
     
     
         6 . The apparatus defined in  claim 1  wherein said antenna comprises an extension of the center conductor beyond the outer conductor and the insulating layer. 
     
     
         7 . The apparatus defined in  claim 6  wherein said extension is tubular and continues said fluid pathway to the outside. 
     
     
         8 . The apparatus defined in  claim 1  wherein said antenna is connected to the center conductor via a connection device at the distal end of the cable. 
     
     
         9 . The apparatus defined in  claim 8  wherein the connection device defines a fluid path between the interior of the center conductor and the outside. 
     
     
         10 . The apparatus defined in  claim 1  wherein the antenna is flexible. 
     
     
         11 . The apparatus defined in  claim 1  and further including a stand-off device adjacent to the distal end of the cable for centering said antenna in a body passage. 
     
     
         12 . The apparatus defined in  claim 1  and further including one or more temperature detectors positioned in said fluid pathway for monitoring coolant temperature at one or more locations therealong. 
     
     
         13 . The apparatus defined in  claim 1  and further including a microwave or RF transmitter connected to said transmit path. 
     
     
         14 . The apparatus defined in  claim 1  and further including a coolant source connected to said second end of the tubular inner conductor of said transmission line segment. 
     
     
         15 . The apparatus defined in  claim 1  wherein said cable and said diplexer are formed as a unitary disposable first part designed for connection both electrically and mechanically to a mating reusable second part containing microwave receiver.