Automatic atherectomy system

Abstract

An automatic atherectomy system uses the rotary burr at the tip of a catheter as a sensing device, in order to measure both the electrical conductivity and permittivity of the surrounding tissue at multiple frequencies. From these parameters it is determined which tissue lies in the different directions around the tip. A servo system steers the catheter tip in the direction of the tissue to be removed. In non-atherectomy applications the rotary tip can be replaced with any desired tool and the system can be used to automatically steer the catheter to the desired position. The steering is done hydraulically, by pressurizing miniature bellows located near the catheter tip.

1 . A method of automatically controlling a tool for removing non-desired tissue from the body without harming desired tissue, said method comprising the steps of:
 discriminating between desired and non desired tissue based on sensing the properties of the tissue adjacent to the tool tip;   automatically steering said tool in the direction of the non-desired tissue; and   eliminating the non-desired tissue.   
   
   
       2 . A method for automated removal of plaque from blood vessels by the use of a rotary tool, said method comprising the steps of:
 discriminating between blood vessel walls, blood and plaque based on sensing the properties of the tissue adjacent to the tool tip;   automatically steering said tool in the direction of the plaque; and   removing the plaque by rotary abrasion.   
   
   
       3 . A method of automatically steering a catheter in a body lumen, said method comprising the steps of:
 discriminating between the wall of said lumen and the inside of said lumen based on sensing the properties of the tissue adjacent to tip of said catheter;   automatically steering tip to avoid damaging said wall.   
   
   
       4 . A method as in  claim 1  wherein said discrimination is based on electrical properties. 
   
   
       5 . A method as in  claim 2  wherein said discrimination is based on electrical properties. 
   
   
       6 . A method as in  claim 3  wherein said discrimination is based on electrical properties. 
   
   
       7 . A method as in  claim 1  wherein said discrimination is based on mechanical properties. 
   
   
       8 . A method as in  claim 2  wherein said discrimination is based on mechanical properties. 
   
   
       9 . A method as in  claim 3  wherein said discrimination is based on mechanical properties. 
   
   
       10 . A method as in  claim 1  wherein said discrimination is based on thermal properties. 
   
   
       11 . A method as in  claim 1  wherein said discrimination is based on the electrical properties of conductivity, permittivity and changes of permittivity with frequency. 
   
   
       12 . A method as in  claim 2  wherein said discrimination is based on the electrical properties of conductivity, permittivity and changes of permittivity with frequency. 
   
   
       13 . A method as in  claim 1  wherein said steering is done hydraulically. 
   
   
       14 . A method as in  claim 2  wherein said steering is done hydraulically. 
   
   
       15 . A method as in  claim 3  wherein said steering is done hydraulically. 
   
   
       16 . A method as in  claim 1  wherein said steering is done by using a magnetic field external to the body. 
   
   
       17 . A method as in  claim 2  wherein said steering is done by using a magnetic field external to the body. 
   
   
       18 . A method as in  claim 3  wherein said steering is done by using a magnetic field external to the body. 
   
   
       19 . A method as in  claim 2  wherein said discrimination is based on the fact that plaque has lower electrical conductivity than blood or blood vessel wall, and the electrical permittivity of blood vessel walls falls faster with frequency than the permittivity of blood. 
   
   
       20 . A method as in  claim 2  wherein the rotary action of the tool is used to scan the different tissues surrounding the tool.