Intravascular imaging catheter tip having a dynamic radius

• US 5,435,314 A
• Filed: 03/25/1994
• Issued: 07/25/1995
• Est. Priority Date: 03/25/1994
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett Packard Company (HP Inc.)
• Inventors: Dias, J. Fleming
• Primary Examiner(s): JAWORSKI, FRANCIS J
• Application Number:
  US08/218,005
• Time in Patent Office: 487 Days
• Field of Search: 128/660.03, 128/660.09, 128/660.1, 128/662.06
• US Class Current: 600/463
• CPC Class Codes: A61B 8/12 in body cavities or body tracts, e.g. by using catheters catheters per se A61M25/00
• CPC Class Codes: A61B 8/445 Details of catheter construction
• CPC Class Codes: A61B 8/4461 Features of the scanning mechanism, e.g. for moving the transducer within the housing of the probe
• CPC Class Codes: G01N 2291/02466 Biological material, e.g. blood
• CPC Class Codes: G01N 2291/101 one transducer
• CPC Class Codes: G01N 2291/2634 cylindrical from outside
• CPC Class Codes: G01N 29/221 Arrangements for directing or focusing the acoustical waves electronic orientation or focusing G01N29/262; sound directing or focusing G10K11/26; mechanical steering of sound transducers or their beams G10K11/35
• CPC Class Codes: G01S 15/8943 co-operating with reflectors
• CPC Class Codes: G01S 7/52047 for elimination of side lobes or of grating lobes; for increasing resolving power
• CPC Class Codes: G10K 11/002 Devices for damping, suppressing, obstructing or conducting sound in acoustic devices G10K1/06 - G10K1/10 take precedence; for electro-mechanical transducers for communication H04R3/002
• CPC Class Codes: G10K 11/357 by moving a reflector

Abstract

A catheter tip imaging probe varies the effective radius of resolution of an acoustic beam by translating the focal length. Varying the effective radius improves the resolution at any point of interest along the arterial walls. The focal length can be dynamically translated by deflecting either the transducer or the mirror in a conventional imaging probe.

Claims

1. An intravascular imaging catheter tip comprising:

catheter housing having a distal end;

a transducer having a focal point that is positioned at a first radius of resolution, the transducer being attached to the distal end of the catheter housing, the transducer emitting a first acoustical wave in response to receiving a first electrical signal and sending a second electrical signal in response to receiving a second acoustical wave;

transmission means for carrying the first and second electrical signals;

a mirror receiving and deflecting the first and second acoustical waves;

rotating shaft that rotates the first and second acoustical waves along a selected radius of resolution; and

translating means, positioned within the distal end of the catheter housing, for shifting the focal point to a second radius of resolution by expanding and contracting.

2. An intravascular imaging catheter tip as defined in claim 1, further comprising:

the translating means being positioned between the transducer and distal end, the translating means shifts the focal point from the first radius of resolution to the second radius of resolution by moving the transducer; and

the rotating shaft being attached to the mirror.

3. An intravascular imaging catheter tip as defined in claim 2, wherein the translating means is a ferroelectric multilayer plug comprising:

a back electrode attached to the distal end of the catheter housing;

a series of ferroelectric layers extending from the back electrode to the transducer;

a plurality of interleaving electrodes, each one interposing two adjacent ferroelectric layers; and

a front electrode connecting between the series and the transducer;

wherein the ferroelectric multilayer plug dynamically shifts the focal point by moving the transducer when an electric field is applied across the back, front and plurality of electrodes.

4. An intravascular imaging catheter tip as defined in claim 2, the translating means comprising a tiny air bellow.

5. An intravascular imaging catheter tip as defined in claim 2, the translating means comprising a porous plug.

6. An intravascular imaging catheter tips defined in claim 2, the translating means comprising an electromechanical actuator.

7. An intravascular imaging catheter tip as defined in claim 2, the translating means comprising a layered ceramic plug.

8. An intravascular imaging catheter tip as defined in claim 1, further comprising the translating means being positioned between the mirror and the rotating shaft, wherein the translating means shifts the focal point from the first radius of resolution to the second radius of resolution by moving the mirror along an axis parallel to the rotating shaft.

9. An intravascular imaging catheter tip as defined in claim 8, wherein the translating means is a ferroelectric multilayer plug comprising:

a back electrode attached to the rotating shaft;

a series of ferroelectric layers extending from the back electrode to the mirror;

a plurality of interleaving electrodes, each one interposing two adjacent ferroelectric layers; and

a front electrode connecting between the series and the mirror;

wherein the ferroelectric multilayer plug dynamically shifts the focal point by moving the mirror when an electric field is applied across the back, front and plurality of electrodes.

10. A method of improving resolution of an intravascular imaging catheter tip having a transducer and a mechanical spring, the method comprising the steps of:

projecting from the transducer an acoustic beam having a focal point at a first radius of resolution along an intravascular wall;

changing the length of the mechanical spring;

translating the focal point to a second radius of resolution along the intravascular wall; and

receiving an image beam.

11. A method of improving resolution as defined in claim 10, wherein the step of translating the focal point comprises moving the transducer.

12. A method of improving resolution as defined in claim 10, wherein:

the step of projecting further comprises projecting the beam onto a mirror; and

the step of translating the focal point comprises moving the mirror linearly.

13. A method of improving resolution as defined in claim 10, wherein the receiving imaging beam is dynamically translated in time.