Intravascular Ultrasound Techniques

• US 20080200815A1
• Filed: 08/11/2005
• Published: 08/21/2008
• Est. Priority Date: 08/13/2004
• Status: Active Grant

• Current Assignee: Stichting Voor de Technische Wetenschappen
• Original Assignee: Stichting Voor de Technische Wetenschappen
• Inventors: Goertz, David Eric, Van Der Steen, Antonius Franciscus Wilhelmus, Frijlink, Martin Egbert
• Granted Patent: US 8,454,520 B2
• Time in Patent Office: Days
• US Class Current: 600/467
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• 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 8/481 involving the use of contrast agent, e.g. microbubbles introduced into the bloodstream analysis of echo signal exploiting properties of a contrast enhancer in devices for short-range imaging with acoustic waves G01S7/52039

Abstract

Intravascular ultrasound techniques provide for intravascular imaging using contrast agents and nonlinear techniques. An ultrasound imaging device for detecting internal properties of a target body comprises an ultrasound transducer positioned at a distal end portion of a catheter, for transmitting excitation pulses and for receiving echo signals. A signal processor analyses echo signals at harmonics and/or subharmonics of the transmit frequency. The catheter may include a contrast agent delivery conduit extending along the catheter, the delivery conduit having an exit orifice proximal to the ultrasound transducer. The device may discriminate between echo signals respectively arising from interaction with tissue and from the interaction with contrast agent. The device may generate an image of the site of interest using non-linear components of the received ultrasound echo signals.

Claims

1. An ultrasound imaging device for detecting internal properties of a target body, comprising:

an ultrasound transducer positioned at a distal end portion of a catheter for intravascular introduction into the target body, the ultrasound transducer having a transmit frequency;

a waveform generator, coupled to the transducer, for producing excitation pulses at the transmit frequency;

a receiver for receiving echo signals from the transducer; and

a signal processor for analysing echo signals at harmonics and/or subharmonics of the transmit frequency.

2. The device of claim 1 in which the transducer and waveform generator are adapted to transmit excitation signals at a frequency in the range 10 to 80 MHz.

3. The device of claim 1 in which the transducer and waveform generator are adapted to transmit excitation signals having a centre frequency in the range 15 to 50 MHz.

4. The device of claim 1 in which the transducer has an active element surface of less than 1 mm in diameter.

5. The device of claim 1 in which the transducer is adapted to produce a steerable excitation beam.

6. The device of claim 5 in which the transducer comprises at least one mechanically steerable active element.

7. The device of claim 5 in which the transducer comprises an array of active elements which can be phased to result in electronic beam steering.

8. The device of claim 1 in which the transducer is adapted to produce acoustic pressures of at least 10 kPa at the transmit frequency.

9. The device of claim 8 in which the transducer is adapted to produce acoustic pressures of at least 100 kPa at the transmit frequency.

10. The device of claim 1 further including a second, lower frequency transducer positioned at the distal end portion of the catheter for producing contrast agent destruction pulses in the range 1 to 15 MHz.

11. The device of claim 10 in which the second transducer is adapted to produce acoustic pressures of at least 200 kPa.

12. The device of claim 1 in which the waveform generator is adapted to generate multiple pulse sequences for stimulating echo signals at the harmonic and/or subharmonic frequencies.

13. The device of claim 1 in which the signal processor includes means for determining the energy at the harmonic and/or subharmonic frequencies by analysis of multiple pulse sequences.

14. An ultrasound imaging device for intravascular ultrasound imaging of a patient'"'"'s body comprising:

a catheter-based ultrasound transducer for insertion into the body at a site of interest;

means for transmitting a series of ultrasound excitation signals from the transducer sufficient to induce a non-linear response in tissue at the site of interest;

means for receiving ultrasound echo signals in response to the excitation signals; and

means for generating an image of the site of interest using non-linear components of the received ultrasound echo signals.

15. An ultrasound transducer head for use with an intravascular ultrasound imaging system for imaging internal parts of a target body, comprising:

an ultrasound transducer positioned at a distal end portion of a catheter for intravascular introduction into the target body; and

a contrast agent delivery conduit extending along the catheter, the delivery conduit having an exit orifice proximal to the ultrasound transducer.

16. The transducer head of claim 15 further including a delivery pump for delivering a predetermined volume of contrast agent through the exit orifice.

17. The transducer head of claim 15 further including a delivery pump for delivering contrast agent through the exit orifice at a predetermined rate.

18. The transducer head of claim 15 in which the ultrasound transducer has an active element surface of less than 1 mm in diameter.

19. The transducer head of claim 15 in which the ultrasound transducer is adapted to produce a steerable excitation beam.

20. The transducer head of claim 19 in which the transducer comprises at least one mechanically steerable active element.

21. The device of claim 19 in which the ultrasound transducer comprises an array of active elements which can be phased to result in electronic beam steering.

22. The device of claim 15 further including a remotely controlled closure mechanism to open and close the exit orifice.

23. The device of claim 15 in which the exit orifice and the active surface of transducer are separated by a distance of between 10 and 300 mm.

24. The device of claim 15 further including a bend in the distal end region of the catheter to provide lateral displacement of the transducer to a position off the axis of a main portion of the catheter.

25. A method of intravascular ultrasound imaging of a patient'"'"'s body comprising the steps of:

introducing a catheter-based ultrasound transducer into the body at a site of interest;

transmitting a series of ultrasound excitation signals from the transducer sufficient to induce a non-linear response in tissue at the site of interest;

receiving ultrasound echo signals in response to the excitation signals;

generating an image of the site of interest using non-linear components of the received ultrasound echo signals.

26. The method of claim 25 wherein the catheter-based ultrasound transducer is a rotating single element transducer.