Implantable surface acoustic wave devices for long term clinical monitoring

• US 8,764,677 B2
• Filed: 12/14/2004
• Issued: 07/01/2014
• Est. Priority Date: 12/15/2003
• Status: Expired

• Current Assignee: IP2IPO Innovations Limited (IP Group plc)
• Original Assignee: Imperial College Innovations Ltd. (Imperial College London)
• Inventors: Toumazou, Christopher, McLeod, Christopher Neil, Vandevoorde, Glenn Noel Robert
• Primary Examiner(s): Dougherty, Sean
• Assistant Examiner(s): Stout, Michael C
• Application Number:
  US10/582,482
• Publication Number:
  US 20070282172A1
• Time in Patent Office: 3,486 Days
• Field of Search: 600/481, 600/486, 600/488, 600/561
• US Class Current: 600/561
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/031 Intracranial pressure
• CPC Class Codes: A61B 8/04 Measuring blood pressure
• 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 8/4472 Wireless probes

Abstract

A surface or bulk acoustic wave device can be implanted in or worn on a human or animal body to monitor various parameters thereof. The device comprises a pair of interdigitated transducers spaced apart over the surface of a piezo-electric substrate that is exposed to the parameter to be monitored. The device is interrogated by a radio-frequency signal being supplied to one of the transducers and detected after reflection by the other transducer. The parameter is measured by comparison of the supplied and received signals.

Claims

1. A method of monitoring cardiovascular or intra-cranial pressure within a human or animal body comprising a surface acoustic wave device implanted therein, wherein the device comprises an interdigitated transducer on the surface of a piezo-electric substrate that closes a sealed chamber to form a transducer body, which substrate is exposed such that the cardiovascular or intra-cranial pressure to be monitored acts on the exposed substrate, wherein an antenna is connected to the interdigitated transducer, wherein a radio-frequency signal is supplied externally of the body to the antenna, is transmitted as a surface acoustic wave over the substrate surface to a reflector on the surface, reflected therefrom back to the said transducer and transmitted from the antenna to an external receiver, whereby comparison of the supplied and received signals provides a measurement of pressure difference across the substrate.

2. A method according to claim 1 wherein the cardiovascular or intra-cranial pressure is monitored by determination of a delay of the surface acoustic wave.

3. A method according to claim 1 wherein the cardiovascular or intra-cranial pressure is monitored by determination of the change of resonant frequency of the surface acoustic wave.

4. A method according to claim 1 wherein a plurality of said devices is employed arranged to operate at different frequencies.

5. A method of monitoring cardiovascular or intra-cranial pressure within a human or animal body, wherein a pair of surface acoustic wave devices is implanted in the body, a first of the devices being a pressure-sensitive acoustic wave device used in the method claimed in any one claim 1, 2, 3 or 4, and a second of the devices being a surface acoustic wave device which is relatively insensitive to the cardiovascular or intra-cranial pressure and being operated as a reference device thereby to cancel any effect on the cardiovascular or intra-cranial pressure measurement of unwanted parameters.

6. A method of monitoring cardiovascular or intra-cranial pressure within a human or animal body comprising an implanted surface acoustic wave device which comprises a pair of interdigitated transducers spaced apart over the surface of a piezoelectric substrate that seals over a chamber to form a transducer body, which substrate is exposed such that the cardiovascular or intra-cranial pressure to be monitored acts on the exposed substrate, wherein an antenna is connected to one of the interdigitated transducers, wherein a radio-frequency signal is supplied externally of the body to the antenna, is transmitted over the substrate surface as an acoustic wave to the other of the transducers, reflected therefrom back to the said one of the transducers and transmitted from the antenna thereof to an external receiver, whereby comparison of the supplied and received signals provides a measurement of the cardiovascular or intra-cranial pressure.