Vascular acoustic emission analysis in a balloon angioplasty system

• US 5,957,950 A
• Filed: 06/13/1997
• Issued: 09/28/1999
• Est. Priority Date: 01/21/1997
• Status: Expired due to Fees

• Current Assignee: Northwestern University
• Original Assignee: Northwestern University
• Inventors: Davidson, Charles, Nagaraj, Ashwin, Fildes, John M., Mockros, Lyle F., Chandran, Krishnan B., Vonesh, Michael J., McPherson, David D.
• Primary Examiner(s): Thaler, Michael H.
• Application Number:
  US08/874,880
• Time in Patent Office: 837 Days
• Field of Search: 606/194, 606/108, 604/96, 600/470, 600/586
• US Class Current: 606/194
• CPC Class Codes: A61B 2017/0011 piezoelectric
• CPC Class Codes: A61M 25/104 used for angioplasty

Abstract

A system and method for performing balloon angioplasty treatment on a patient. The system includes a catheter for insertion into an artery of the patient, a balloon coupled to the catheter with the balloon expandable by fluid passed through the catheter in order to apply pressure to plaque lesions deposited on vascular tissue of the artery. The balloon includes a PVDF piezoelectric transducer for sensing acoustic emission signals generated by deformation of the plaque lesions and the vascular tissue. The acoustic emission signals can be analyzed by frequency analysis, time domain analysis and wavelet analysis followed by neural net correlation evaluation.

Claims

1. A system for performing angioplasty treatment on a patient, comprising:

a catheter for insertion into and through an artery of the patient;

means consisting solely of a mechanical device coupled to the catheter for applying mechanical energy to atherosclerotic plaque lesions deposited on and within said vascular tissue of the artery and also for creating acoustic emission signals arising solely from mechanical displacement of the lesions and said vascular tissue, said device expandable by fluid passed through the catheter in order to apply mechanical pressure to plaque lesions coupled to said vascular tissue of the artery and to cause at least one of (a) deformation of the plaque lesions, (b) cracking of the plaque lesions, (c) stretching of said vascular tissue and (d) rupture of said vascular tissue;

a transducer for sensing acoustic emission signals arising solely from expansion of the device to cause at least one of (a) deformation of the plaque lesions, (b) cracking of the plaque lesions, (c) stretching of said vascular tissue and (d) rupture of said vascular tissue; and

means for evaluating the acoustic emission signals arising solely from the mechanical device coupled to the catheter applying mechanical pressure to the plaque lesions and the artery to determine which of the categories (a), (b), (c), and (d) said acoustic emission signals belong.

2. The system as defined in claim 1 wherein said transducer comprises a PVDF film included with said mechanical device.

3. The system as defined in claim 1 wherein said mechanical device is comprised at least in part of PVDF.

4. The system as defined in claim 1 wherein said transducer is disposed between an overlying metal layer and an underlying metal layer coupled to an exterior surface of said mechanical device.

5. The system as defined in claim 1 wherein said transducer is disposed between an overlying metal layer and an underlying metal layer coupled to an interior surface of said mechanical device.

6. The system as defined in claim 1 wherein said transducer comprises a matrix of piezoelectric material bands included with said balloon.

7. The system as defined in claim 1 wherein said transducer is disposed within said balloon and at least one of (a) on an interior surface of said catheter, (b) and an exterior surface of said catheter, and (c) integrally part of said catheter.

8. The system as defined in claim 1 further including at least one transducer coupled to said catheter for differential analysis of the acoustic emission signals in conjunction with said piezoelectric transducer included with said balloon.

9. The system as defined in claim 1 wherein said transducer comprises a non-invasive transducer adapted to be disposed on the chest wall of the patient.

10. The system as defined in claim 1 further including indicator means for informing a physician who is implementing the angioplasty treatment that an angioplasty event has occurred, thereby enabling the physician to selectively modify the balloon angioplasty treatment.

11. The system as defined in claim 10 wherein the means for informing comprises at least one of a speaker for outputting a sound spectrum characteristic of said angioplasty event and a display for showing the acoustic emission signals characteristic of said angioplasty event.

12. The system as defined in claim 1 further including means for automatically terminating the angioplasty treatment upon onset of vascular rupture.

13. The system as defined in claim 12 wherein said means for automatically terminating comprises an automatic pressure relief component for the fluid passed through said catheter.

14. The system as defined in claim 1 wherein said means for evaluating includes computer means for executing a Fourier transform computer program to convert a time varying form of said acoustic emission signals to a frequency amplitude spectrum for analysis of the balloon angioplasty treatment.

15. The system as defined in claim 14 further including a display for generating at least a two dimensional image of said frequency amplitude spectrum for analysis of the angioplasty treatment.

16. A system for performing angioplasty treatment on a patient, comprising:

a catheter for insertion into and through an artery of the patient;

a mechanical device coupled to said catheter, said mechanical device expandable by fluid passed through said catheter in order to apply pressure to atherosclerotic plaque lesions coupled to vascular tissue of the artery;

said system including a transducer for sensing acoustic emissions signals generated by said mechanical device causing at least one of (a) deformation, of the plaque lesions, (b) cracking of the plaque lesions, (c) stretching of the vascular tissue and (d) rupture of the vascular tissue; and

computer means for executing a computer program for analyzing said acoustic emissions signals arising solely from the mechanical device expansion causing at least one of (a) deformation of the plaque lesions, (b) cracking of the plaque lesions, (c) stretching of the vascular tissue and (d) rupture of the vascular tissue, said computer program operating on said acoustic emission signals to determine which of the categories (a), (b), (c) and (d) said acoustic emission signals belong.

17. The system as defined in claim 16 further including an A/D converter for generating a digitized data form of said acoustic emission signals and wherein said computer means comprises means responsive to said digitized data form for forming an overlapping series of Fourier transformed acoustic emission signals for input to a neural network computer program for analysis of the category in which said acoustic emission signals belong.

18. The system as defined in claim 16 further including means for automatically varying the pressure applied to the vascular tissue responsive to the analysis of said acoustic emission signals.

19. A method for performing angioplasty treatment on a patient, comprising the steps of:

inserting a catheter into and through an artery of the patient, said catheter including a balloon positioned in a region of the artery having atherosclerotic plaque lesions coupled to interior walls of the artery;

inflating said balloon to apply pressure to the plaque lesions causing at least one of (a) deformation of the plaque lesions, (b) cracking of the plaque lesions, (c) stretching of the artery and (d) rupture of the artery and further causing generation of acoustic emission signals arising solely from inflating said balloon to cause at least one of (a) deformation of the plaque lesions, (b) cracking of the plaque lesions, (c) stretching of the artery and (d) rupture of the artery;

sensing said acoustic emissions signals using sensors;

outputting said sensed acoustic emission signals to a computer; and

executing computer programs to analyze said acoustic emission signals to carry out analysis of the angioplasty treatment.

20. The method as defined in claim 19 further including the step of performing Fourier transformations of said acoustic emission signals before performing analysis of said acoustic emissions signals.

21. The method as defined in claim 19 further including the step of performing frequency filtration of said acoustic emission signals to generate wavelets for analysis by a step of performing a neural network analysis.

22. A method for performing angioplasty treatment and deploying a stent in an artery of a patient, comprising the steps of:

inserting a catheter into and through an artery of the patient, said catheter including a balloon and an attached deployable stent positioned in a region of the artery having atherosclerotic plaque lesions coupled to interior walls of the artery;

inflating said balloon and deploying said stent to be in full apposition to the interior walls of the artery, said balloon applying pressure to the plaque lesions causing at least one of (a) deformation of the plaque lesions, (b) cracking of the plaque lesions, (c) stretching of the artery and (d) rupture of the artery and further causing generation of acoustic emission signals associated with (a) deformation of the plaque lesions, (b) cracking of the plaque lesions, (c) stretching of the vascular tissue of the artery and (d) rupture of vascular tissue of the artery and characterizing position of the stent relative to the walls of the artery;

sensing said acoustic emission signals using a sensor;

outputting said sensed acoustic emission signals to a computer; and

executing a computer program using said computer to analyze said acoustic emission signals arising solely from the step of inflating the balloon which causes at least one of (a) deformation of the plaque lesions, (b) cracking of the plaque lesions, (c) stretching of the artery and (d) rupture of the artery to carry out analysis of the balloon angioplasty treatment and to help determine the position of said stent relative to the walls of the artery.