Sonic element and catheter incorporating same

• US 6,669,655 B1
• Filed: 10/19/2000
• Issued: 12/30/2003
• Est. Priority Date: 10/20/1999
• Status: Expired due to Term

• Current Assignee: Recor Medical, Inc. (Otsuka Holdings Company Limited)
• Original Assignee: Transurgical, Inc.
• Inventors: Novak, Alfred, Acker, David E.
• Primary Examiner(s): PAIK, SANG YEOP
• Application Number:
  US09/691,825
• Time in Patent Office: 1,167 Days
• Field of Search: 601/2, 601/3, 601/4, 600/437, 600/439, 600/459, 600/462, 600/466, 600/470, 600/471, 607/96, 607/98, 607/99
• US Class Current: 601/2
• CPC Class Codes: A61B 17/2202 the ultrasound transducer being inside patient's body at the distal end of the catheter
• CPC Class Codes: A61B 2017/00243 cardiac
• CPC Class Codes: A61B 2017/22028 arrays, e.g. phased arrays
• CPC Class Codes: A61N 2007/0065 Concave transducers
• CPC Class Codes: A61N 2007/027 with multiple foci created simultaneously
• CPC Class Codes: A61N 7/02 Localised ultrasound hyperthermia hyperthermia in general A61F7/00
• CPC Class Codes: A61N 7/022 intracavitary

Abstract

A catheter carrying a radially-expansible ultrasonic transducer is threaded into the circulatory system and then the transducer is actuated to provide ultrasonic energy in a ring-like zone surrounding a blood vessel. Desirably, the transducer is arranged to focus the ultrasonic energy into a narrow, ring-like focal zone having an extent, in the axial direction along the catheter, less than the axial extent of the transducer. The transducer desirably is expanded after threading so that during application of the ultrasonic energy, the transducer bears on the interior wall of a blood vessel through a balloon covering the transducer. The transducer may include one or more resilient spiral elements carrying a flexible piezoelectric material.

Claims

1. A sonic emitting element comprising a piezoelectric element having a radiating surface in the form of a surface of revolution of a generatrix about a central axis, said generatrix including a minimum point at a minimum distance from said central axis, a first portion sloping away from the axis in a first axial direction from said minimum point, and a second portion sloping away from said central axis in a second axial direction from said minimum point.

2. An element as claimed in claim 1, wherein said first and second portions of said generatrix are curved.

3. An element as claimed in claim 2, wherein said first and second portions of said generatrix are segments of a circle, whereby said radiating surface is in the form of a portion of a toroidal surface.

5. An element as claimed in any of claims 1, 2, 3 and 4 wherein said piezoelectric element is formed from a polymeric piezoelectric material.

6. An element as claimed in claim 1 wherein said piezoelectric element has a maximum diameter of about 1 cm or less.

7. A catheter comprising an element as claimed claim 6, and an elongated catheter body having a proximal end, a distal end and a longitudinal axis extending between said ends, said element being mounted to said body remote from said proximal end so that said central axis of said element is substantially parallel with the longitudinal axis of the catheter body.

8. A catheter as claimed in claim 7, further comprising a balloon surrounding said element and said catheter.

9. A catheter as claimed in claim 8, wherein said balloon is substantially in the form of a surface of revolution about the longitudinal axis of the catheter.

4. An element comprising a piezoelectric element having a radiating surface in the form of a portion of a toroidal surface having a central axis, said portion of said toroidal surface facing outwardly away from said central axis, whereby said emitting element will focus emitted sonic energy in a generally circular band surrounding the element.

10. A method of treating tissue within the body of a subject comprising the steps of:

(a) threading a catheter into a circulatory system of the subject so that a emitting element carried on said catheter is positioned within a circulatory vessel with a central axis of the emitting element substantially aligned with an axis of the circulatory vessel, said emitting element having an axial length in a direction along said central axis;

(b) actuating said emitting element to emit sonic energy in a pattern which is generally symmetrical about said central axis, said sonic energy being emitted so that the sonic waves from different portions of said emitting element intersect and mutually reinforce one another in a ring-like focal region surrounding said central axis, said focal region having an axial length less than the axial length of said emitting element.

11. A method as claimed in claim 10, wherein sonic energy from different portions of the emitting element along the axial extent of emitting element is directed at different angles to the central axis of the radiating element.

12. A method as claimed in claim 10 wherein said actuating step is performed for a time sufficient to ablate tissue in said focal region.

13. A method as claimed in claim 12 wherein tissue disposed outside of said focal region is not ablated.

14. A method as claimed in claim 10 wherein said circulatory vessel is a blood vessel communicating with a chamber of the heart and wherein the emitting element is disposed adjacent the juncture of such blood vessel and the heart.