WO2004004559A1

WO2004004559A1 - Low profile chest affixed cw transducer

Info

Publication number: WO2004004559A1
Application number: PCT/AU2003/000806
Authority: WO
Inventors: Robert Allan Phillips
Original assignee: Uscom Pty Ltd
Priority date: 2002-07-03
Filing date: 2003-06-26
Publication date: 2004-01-15
Also published as: AUPS335402A0

Abstract

An ultrasonic transducer device comprising: at least one electrically deformable electrode having a first planar substrate; a profiled wedge having a first surface substantially mating with the first planar substrate and a second surface profiled so as to mate with the chest wall of a patient; wherein the profiled wedge thereby holds the electrically deformable electrode in a predetermined angular relationship to the chest wall of the patient.

Description

Low Profile Chest Affixed CW Transducer

Field of the Invention

The present invention relates to the field of ultrasonic transducers and, in particular, discloses a low profile ultrasonic transducer for use in ultrasonic monitoring of bodily functions such as blood-flow.

Background of the Invention

It has recently been proposed to utilise ultrasound techniques in the continuous monitoring of bodily functions such as cardiac bloodflows or the like.

In order to provide continuous cardiac monitoring, it is preferable to have a stable monitoring element that can be utilised in monitoring for extended periods of time. It is further preferable that the transducer has a low profile in order that it be as unobtrusive as possible. This provides added comfort to the patient and prevents the transducer from being inadvertently displaced.

Summary of the Invention

It is an object of the present invention to provide an improved transducer device suitable for use in continuous monitoring operations.

In accordance with a first aspect of the present invention, there is provided an ultrasonic transducer device comprising: at least one electrically deformable electrode having a first planar substrate; a profiled wedge having a first surface substantially mating with the first planar substrate and a second surface profiled so as to mate with the chest wall of a patient; wherein the profiled wedge thereby holds the electrically deformable electrode in a predetermined angular relationship to the chest wall of the patient.

Preferably, the number of deformable electrodes is two and the profiled wedge includes: a first surface substantially mating with the first planar substrate; a second surface substantially mating with a second planar substrate of a second electrode; and wherein the profiled wedge thereby holds the first and second substrate in a predetermined angular relationship to one another such that the device has a focus point formed a predetermined distance inside a patient. The wedge can be profiled so that the planar substrate forms an angle of approximately 20 degrees with the wall of a patient. hi a further aspect, the present invention resides in a transducer device including a mounting portion having an aperture defined therein and defining a substantially planar mounting face for mounting to an insonation surface, and a raised body portion extending from the mounting portion, the body portion together with the aperture defining a cavity, and one or more acoustic transducer elements housed within the cavity, wherein the transducer elements are mounted obliquely within the cavity relative to the mounting face to provide an acoustic beam through the aperture such that the acoustic beam is angled obliquely to the mounting face of the mounting portion.

Preferably the one or more transducer elements are disposed in the cavity such that a gap is provided between the one or more transducer elements and a wall of the body portion, the gap being on an opposite side of the one or more transducer elements to the aperture. A single, double or multi-faceted wedge of acoustic coupling material may be interposed between the mounting face and the one or more transducer elements, the wedge defining at least one angled face for mounting the one or more transducer elements obliquely to the mounting surface.

Conveniently, the planar mounting portion is in the form of an annular disc. Preferably, the body portion includes an aperture in a side wall for receiving one or more leads of the one or more transducer elements.

Preferably, at least two transducer elements are provided, which are typically inclined with respect to each other so as to provide a pair of intersecting acoustic beams defining a target zone a predetermined depth beneath the insonation surface. In a further aspect, the present invention resides in a transducer device including a mounting portion having an aperture defined therein and defining a substantially planar mounting face for mounting to an insonation surface, a raised body portion extending from the mounting portion, the body portion together with the aperture defining a cavity, and one or more CW Doppler acoustic transducer elements housed within the cavity, wherein the transducer elements are mounted obliquely within the cavity relative to the mounting face to provide an acoustic beam through the aperture such that the acoustic beam is angled obliquely to the mounting face of the mounting portion. In a further aspect, the present invention resides in a transducer device including a mounting portion having an aperture defined therein and defining a substantially planar mounting face for mounting to an insonation surface, and a raised body portion extending from the mounting portion, the body portion together with the aperture defining a cavity, and one or more acoustic transducer elements housed within the cavity, wherein the transducer elements are mounted obliquely within the cavity relative to the mounting face to provide an acoustic beam through the aperture such that the acoustic beam is angled obliquely to the mounting face of the mounting portion, and wherein the transducer device may be mounted to a patient to provide substantially hands free monitoring of patient blood flow.

Brief Description of the Drawings

The invention will now be described by way of example only with reference to preferred embodiments and to the accompanying features in which:-

Fig. 1 is a perspective view of a transducer device of the preferred embodiment; Fig. 2 is a cross-sectional side view of the transducer device of the preferred embodiment of Fig. 1;

Fig. 3 is a perspective view of a pair of acoustic transducer elements;

Fig. 4 is a side perspective view of the adhesive mount;

Figs. 5 and 6 are schematic views showing intersecting beams from two alternative arrangement of transducer elements; and

Fig. 7 shows an embodiment of a transducer mounting wedge in an alternative embodiment.

Detailed Description of the Embodiments i Fig. 1 and 2 there is shown generally at 10 a low-profile CW transducer device according to a preferred embodiment of the present invention. The transducer device 10 includes a planar mounting portion in the form of an annular disc 11 that provides a mounting surface 12 for affixation to an insonation surface via an annular adhesive mount 42. In particularly preferred embodiments, the device 10 is used for monitoring of trans-pulmonary or trans-aortic blood flows and is thus adapted to be affixed to the chest wall of a patient. The mounting portion 11 is a disc-shaped member approximately 4.5 to 6 cm diameter having a central aperture 44 of approximately 1.8 cm in diameter. An integrally moulded body portion 14 extends from the mounting portion 11 around the circumference of the aperture 13. The body section 14 includes a circumferential frusto- conical side wall 15 and a rear wall 16. The side wall 15 is inclined with respect to the mounting portion 11 such that the inner surface of the side wall 15 is oblique to the mounting surface 12. The side wall 15 and rear wall 16 of the body portion together with the aperture 44 defines a cavity 17.

One or more (preferably two) acoustic transducer elements 18 are housed within the cavity 17. The transducer elements 18 are typically in the form of a split CW

Doppler piezo-electric crystal, and of appropriate frequency for the intended application, eg 1-10 MHz for medical applications. The transducer elements divide the cavity 17 into an outer cavity 24 and inner cavity 20. The transducer leads are interconnected to each surface of the transducer element 18 so as to form a circuit. A first lead 40 is connected to the back surface. The second lead e.g. 41 is connected to the other surface along the circumferential rim thereof. The transducer leads extend from the transducer elements 18 into the inner cavity 20 and pass through an aperture 22 in the side wall 15 of the body portion 14.

Referring to Fig. 3, the transducer elements 18 include first and second hemi- cylindrical elements 30 and 31, the diameter of which is approximately 1.8 centimetres, so as to match the size of the aperture 13 and the diameter of the cavity. Each have a separate transmit and receive function.

Turning now to Fig. 4, there is shown the adhesive mount disk 42 in more detail. The adhesive mount 42 is an annular double-sided hypo-allergenic adhesive that on one side affixes to the mounting portion with the central aperture of the adhesive mount aligning with the aperture 44 of the transducer device. The other side of the adhesive mount affixes to the insonation surface, eg the chest of the patient.

The profiling angle on the surface can be adjusted in accordance with the requisite depth of isonation required. If the subject vessel is shallow, such as in a neonatal application, a steep angulation on surfaces 51, 52 of approximately 10° is required in order to produce a shallow intersection beam, eg 5cm from the transducer elements 30 and 31, as is shown in Fig. 5. For deeper applications, for example adult intra-cardiac flow, a lower inclination angle on surfaces 51, 52 is required of approximately 5° to produce a deeper intersection zone of 10cm, as is shown in Fig. 6. Returning to Fig. 2, the transducer elements are secured in place by means of a spacing wedge 26 of acoustic coupling material. The wedge 26 has a transducer mounting surface 25 for attachment of the transducer elements 18, and an affixation surface that communicates with the insonation surface through an acoustic coupling gel

27. hi an alternative version, the transducer elements 18 may be mounted to the housing, with the coupling gel occupying the wedge space.

The device supports and maintains the transducer elements 18 in correct alignment with the targeted flow, such that the ultrasound beam is transmitted obliquely through the surface on which the transducer device is mounted. The device is designed for particular application on the parasternal and apical transthoracic windows for evaluation of trans-pulmonary and trans-aortic blood flow. In such applications a wedge angle of 20 degrees is preferred. An airgap of approximately two to four millimetres is formed in the rear cavity

20 provided behind the acoustic transducer elements 18. This airgap provides air dampening of the acoustic signal.

In alternative embodiments, the transducer elements can be inclined with respect to one another. Such an inclination allows for accurate targeting of the CW-Doppler beam to a particular depth from a patient's body. This is illustrated in Fig. 5 and Fig. 6 wherein the depth maximum beam cross over is altered by altering the inclination angle between transducers 31, 32. Such an inclination can be achieve by mounting the transducers on an appropriately profiled spacer element such as that illustrated 50 in Fig.

7. The transducer arrangement described provides for effective and compact isonation of ultrasound signals especially those used in the long term monitoring of cardiac flow signals.

It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention. The foregoing describes embodiments of the present invention and modifications, obvious to those skilled in the art can be made thereto, without departing from the scope of the present invention.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. An ultrasonic transducer device for use in monitoring flow within a patient, said device comprising:

at least one first electrically deformable electrode having a first planar substrate;

a profiled wedge having a first surface substantially mating with said first planar substrate and a second surface profiled so as to mate with the chest wall of a patient; wherein said profiled wedge thereby holds the electrically deformable electrode in a predetermined angular relationship to the chest wall of a patient.

2. A device as claimed in claim 1 wherein the number of deformable electrodes is two and said profiled wedge includes:

a first surface substantially mating with said first planar substrate;

a second surface substantially mating with a second planar substrate of a second electrode; and

wherein said profiled wedge thereby holds said first and second substrate in a predetermined angular relationship to one another such that ultrasonic emissions from the first and second electrodes of said device have a focal point formed a predetermined distance inside a patient.

3. A device as claimed in claim 1 wherein said predetermined angular relationship between the planar substrate and the chest wall of a patient is substantially 20 degrees.

4. A transducer device including a mounting portion having an aperture defined therein and defining a substantially planar mounting face for mounting to an insonation surface, and a raised body portion extending from said mounting portion, said body portion together with said aperture defining a cavity, and one or more acoustic transducer elements housed within said cavity, wherein said transducer elements are mounted obliquely within said cavity relative to the mounting face to provide an acoustic beam through said aperture such that said acoustic beam is emitted at an angle obliquely to the mounting face of said mounting portion.

5. A transducer device according to claim 4 wherein said one or more transducer elements are disposed in said cavity such that a gap is provided between said one or more transducer elements and a wall of said body portion, said gap being on an opposite side of said one or more transducer elements to said aperture.

6. A transducer device according to claim 4 or 5 wherein a single, double or multi-faceted wedge of acoustic coupling material is interposed between said mounting face and said one or more transducer elements, said wedge defining at least one angled face for mounting said one or more transducer elements obliquely to said mounting surface.

7. A transducer device according to any preceding claim 4 to 6 wherein said planar mounting portion is in the form of an annular disc.

8. A transducer device according to any preceding claim 4 to 8 wherein said body portion includes an aperture in a side wall for receiving one or more leads of said one or more transducer elements.

9. A transducer device according to any preceding claim 4 to 8 wherein at least two transducer elements are provided and are inclined with respect to each other so as to provide for the emission of a pair of intersecting acoustic beams defining a target zone a predetermined depth beneath the insonation surface.

10. A transducer device including a mounting portion having an aperture defined therein and defining a substantially planar mounting face for mounting to an insonation surface, a raised body portion extending from said mounting portion, said body portion together with said aperture defining a cavity, and one or more CW Doppler acoustic transducer elements housed within said cavity, wherein said transducer elements are mounted obliquely within said cavity relative to the mounting face to provide an acoustic beam through said aperture such that said acoustic beam is angled obliquely to the mounting face of said mounting portion.

11. A transducer device including a mounting portion having an aperture defined therein and defining a substantially planar mounting face for mounting to an insonation surface, and a raised body portion extending from said mounting portion, said body portion together with said aperture defining a cavity, and one or more acoustic transducer elements housed within said cavity, wherein said transducer elements are mounted obliquely within said cavity relative to the mounting face to provide an acoustic beam through said aperture such that said acoustic beam is angled obliquely to the mounting face of said mounting portion, and wherein said transducer device maybe mounted to a patient to provide substantially hands free monitoring of blood flow within the patient.

12. A transducer device substantially as hereinbefore described with reference to the accompanying figures.