Devices and methods for renal denervation and assessment thereof

Abstract

The present invention, in some embodiments thereof, relates to a devices and methods for intravascular denervation and assessment thereof and, more particularly, but not exclusively, to devices and methods for renal denervation. Some embodiments of the invention relate to an intravascular catheter configured for ultrasonic ablation of the tissue, comprising a plurality of piezoelectric transceivers. In some embodiments, an intravascular distancing device is provided, the device adapted for obtaining at least a minimal distance between an ultrasound emitting element and a tissue, such as the blood vessel wall. Some embodiments of the invention relate to assessment of renal sympathetic denervation (RSD) treatment effectiveness. Some embodiments of the invention relate to processing echo of signals, such as processing of signals to characterize physical and/or mechanical properties of the blood vessel.

What is claimed is: 
     
         1 . A method of thermally damaging nerves, comprising:
 introducing into an artery a catheter comprising a plurality of rectangular ultrasound transducers, each transducer comprising an emitting surface having an axial length of between 3-8 mm and a width of between 0.5-1.5 mm;   exciting the plurality of ultrasound transducers to generate an acoustic field which sets a thermal effect in nerve tissue located at a radial distance of between 2-15 mm from said emitting surface of each of said rectangular ultrasound transducers.   
     
     
         2 . The method according to  claim 1 , wherein said emitting surface of each of said rectangular ultrasound transducers has an axial length of 6 mm and a width of 1 mm. 
     
     
         3 . The method according to  claim 1 , wherein said emitting surface of each of said rectangular ultrasound transducers has an axial length of 3 mm and a width of 0.7 mm. 
     
     
         4 . The method according to  claim 1 , wherein said emitting surface of each of said rectangular ultrasound transducers has one of: an axial length of 6 mm and a width of 1 mm, an axial length of 3 mm and a width of 0.7 mm. 
     
     
         5 . The method according to  claim 1 , wherein a thickness of each of said rectangular ultrasound transducers is 1 mm. 
     
     
         6 . The method according to  claim 1 , wherein said exciting comprises generating an acoustic field which raises a temperature of said nerve tissue to between 47-55 degrees Celsius. 
     
     
         7 . The method according to  claim 1 , wherein said exciting comprises generating an acoustic field including high intensity regions of between 20 W/cm{circumflex over ( )}2 to 80 W/cm{circumflex over ( )}2. 
     
     
         8 . The method according to  claim 1 , wherein said exciting comprises exciting the plurality of ultrasound transducers to generate a corresponding plurality of trapezoidal beams, wherein dimensions of each of said trapezoidal beams are determined, at least in part, by said axial length and width of said emitting surface. 
     
     
         9 . The method according to  claim 8 , wherein each of said trapezoidal beams diverges at an angle of between 5-20 degrees. 
     
     
         10 . The method according to  claim 1 , wherein said exciting comprises activating said plurality of transducers at a frequency of between 7-14 MHz. 
     
     
         11 . The method according to  claim 1 , wherein said exciting comprises activating said plurality of transducers at a frequency within 10% of a transducer's resonant frequency. 
     
     
         12 . The method according to  claim 1 , wherein said exciting comprises activating said plurality of transducers at an intensity of between 30-40 W/cm{circumflex over ( )}2. 
     
     
         13 . The method according to  claim 1 , wherein said exciting comprises activating said plurality of transducers for a duration of between 5-20 seconds. 
     
     
         14 . The method according to  claim 1 , wherein said exciting comprises activating said plurality of transducers separately yet simultaneously. 
     
     
         15 . The method according to  claim 1 , wherein said introducing comprises positioning said plurality of rectangular ultrasound transducers at a distance of 1 mm or longer from a wall of said artery. 
     
     
         16 . The method according to  claim 15 , wherein said catheter comprises an expandable distancing device and wherein said introducing comprises expanding said distancing device to push said plurality of rectangular ultrasound transducers away from said artery wall. 
     
     
         17 . The method according to  claim 1 , wherein said artery is the renal artery. 
     
     
         18 . An intravascular catheter comprising an elongated shaft and a head for ultrasonic transmission, said head comprising a plurality of ultrasound transducers, wherein each of said ultrasound transducers comprises an emitting surface having either: an axial length of 6 mm and a width of 1 mm; an axial length of 3 mm and a width of 0.7 mm. 
     
     
         19 . The intravascular catheter according to  claim 18 , wherein each of said plurality of ultrasound transducers emits a trapezoidal beam having a depth measured between the bases of the trapezoidal beam of between 1-15 mm. 
     
     
         20 . The intravascular catheter according to  claim 18 , wherein said catheter head is triangular and wherein said plurality of ultrasound transducers are fully fitted within a notional circumscribing circle of the catheter having a diameter of 2.2 mm or smaller.