Methods and devices for heating fluid in fluid enhanced ablation therapy

Abstract

Devices and methods for efficiently and reproducibly heating fluid for use in fluid enhanced ablation are disclosed herein. In one embodiment, an ablation device is provided having an elongate body, at least one wire extending through an inner lumen of the elongate body, and at least one spacer disposed within the inner lumen. The at least one wire extends through the at least one spacer such that the at least one spacer is effective to maintain an adjacent portion of the at least one wire in a substantially fixed geometric relationship with the inner lumen, thereby preventing electrical shorts and providing for the consistent and uniform heating of fluid flowing through the inner lumen of the elongate body.

What is claimed is: 
     
         1 . An ablation device, comprising:
 an elongate body having
 proximal and distal ends, 
 an inner lumen extending through the elongate body, and 
 at least one outlet port formed in the elongate body configured to deliver fluid to tissue surrounding the elongate body; 
   at least one wire extending through the inner lumen, the at least one wire being configured to heat fluid flowing through the inner lumen; and   at least one spacer disposed within the inner lumen, the at least one wire extending through the at least one spacer such that the at least one spacer is effective to maintain an adjacent portion of the at least one wire in a substantially fixed geometric relationship with the inner lumen.   
     
     
         2 . The ablation device of  claim 1 , further comprising an ablation element disposed along a length of the elongate body adjacent to the at least one outlet port, the ablation element being configured to heat tissue surrounding the ablation element when the elongate body is inserted into tissue. 
     
     
         3 . The ablation device of  claim 2 , wherein the at least one wire and the at least one spacer are positioned proximal of the ablation element. 
     
     
         4 . The ablation device of  claim 1 , wherein the at least one spacer comprises a first spacer positioned at a proximal end of a distal portion of the at least one wire, and a second spacer positioned at a distal end of the distal portion of the at least one wire. 
     
     
         5 . The ablation device of  claim 4 , wherein the first and second spacers are positioned a distance apart from one another, and wherein the distance is about 5 mm. 
     
     
         6 . The ablation device of  claim 1 , wherein the at least one spacer comprises a disc-shaped member and the at least one wire comprises first and second wires configured to extend through first and second bores in the spacer. 
     
     
         7 . The ablation device of  claim 1 , wherein the at least one spacer prevents the at least one wire from contacting the inner lumen. 
     
     
         8 . The ablation device of  claim 1 , wherein the at least one spacer has a maximum outer diameter that is less than a diameter of the inner lumen such that the at least one spacer can move radially within the inner lumen. 
     
     
         9 . The ablation device of  claim 1 , wherein the at least one spacer has a maximum outer diameter equal to a diameter of the inner lumen such that the at least one spacer cannot move radially within the inner lumen. 
     
     
         10 . The ablation device of  claim 4 , wherein a portion of the at least one wire extending between the first and second spacers is configured to heat fluid flowing through the inner lumen. 
     
     
         11 . The ablation device of  claim 10 , wherein the first and second spacers are positioned a distance apart from one another, and wherein the distance is about 2 mm. 
     
     
         12 . The ablation device of  claim 1 , wherein the at least one wire is insulated proximal to the at least one spacer. 
     
     
         13 . The ablation device of  claim 1 , wherein the inner lumen is lined with an insulating layer to prevent the at least one wire from contacting an inner wall of the elongate body. 
     
     
         14 . The ablation device of  claim 1 , wherein the at least one spacer is configured to maintain the at least one wire in a position substantially coaxial with a longitudinal axis of the elongate body. 
     
     
         15 . The ablation device of  claim 1 , wherein the at least one spacer comprises at least one protrusion formed on the at least one wire. 
     
     
         16 . The ablation device of  claim 1 , further comprising at least one temperature sensor disposed within the inner lumen distal to the at least one spacer and configured to measure a temperature of the fluid flowing through the inner lumen. 
     
     
         17 . The ablation device of  claim 16 , further comprising a second temperature sensor disposed within the inner lumen proximal to the at least one spacer and configured to measure a temperature of the fluid flowing through the inner lumen. 
     
     
         18 . The ablation device of  claim 16 , wherein the at least one temperature sensor is a thermocouple. 
     
     
         19 . The ablation device of  claim 16 , wherein the at least one temperature sensor is separated from the at least one spacer by a distance of about 10 mm. 
     
     
         20 . The ablation device of  claim 16 , wherein the at least one temperature sensor is separated from the at least one spacer by a distance of about 2 mm. 
     
     
         21 . A method of ablating tissue, comprising:
 inserting an elongate body into a tissue mass;   delivering fluid through an inner lumen of the elongate body, the fluid flowing through at least one outlet port in the elongate body and into the tissue mass; and   delivering energy through at least one wire extending through the inner lumen to heat the fluid within the lumen to a predetermined temperature.   
     
     
         22 . The method of  claim 21 , wherein delivering energy through at least one wire comprises passing energy between two or more wires extending through the inner lumen. 
     
     
         23 . The method of  claim 21 , wherein delivering energy through at least one wire comprises passing energy between one or more wires and the elongate body. 
     
     
         24 . The method of  claim 21 , wherein delivering energy through at least one wire comprises passing energy between one or more wires and a conductive tube contained within the elongate body. 
     
     
         25 . The method of  claim 21 , further comprising delivering energy into the tissue mass from at least one ablation element positioned adjacent to the at least one outlet port. 
     
     
         26 . A method for manufacturing a plurality of ablation devices, comprising:
 forming a first ablation device by positioning a first heating assembly within a first elongate body, the first heating assembly having at least one wire extending through at least one spacer; and   forming a second ablation device by positioning a second heating assembly within a second elongate body, the second heating assembly having at least one wire extending through at least one spacer;   wherein an electrical resistance of the first heating assembly is substantially identical to an electrical resistance of the second heating assembly.   
     
     
         27 . An ablation device, comprising:
 an elongate body having
 proximal and distal ends, 
 an inner lumen extending through the elongate body, and 
 at least one outlet port formed in the elongate body configured to deliver fluid to tissue surrounding the elongate body; 
   a heating assembly comprising at least two wires extending through the inner lumen, the at least two wires being configured to heat fluid flowing through the inner lumen; and   at least one spacer disposed within the inner lumen, the at least two wires extending through the at least one spacer such that the at least one spacer is effective to maintain the at least two wires in a substantially fixed geometric relationship with each other.   
     
     
         28 . The ablation device of  claim 27 , further comprising an ablation element disposed along a length of the elongate body adjacent to the at least one outlet port, the ablation element being configured to heat tissue surrounding the ablation element when the elongate body is inserted into tissue.