Surgery – Truss – Pad
Patent
1994-01-31
1995-10-10
Jaworski, Francis
Surgery
Truss
Pad
12866206, A61B 812
Patent
active
054562597
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an ultrasonic transducer arrangement and catheter and more particularly to one for use in a system of the kind disclosed in our international patent application WO89/04142.
BACKGROUND OF THE INVENTION
In that patent application there is disclosed a system for visualising internal human organs by means of an invasive ultrasonic technique.
In that system ultrasonic signals are generated and received by a transducer assembly mounted on the distal end of a catheter to be inserted into the patient. The present invention is concerned with the construction and manufacture of such a transducer arrangement and catheter.
The transducer arrangement of that earlier patent application consists essentially of a cylindrical array of piezo-electric crystal transducer elements. In the embodiment described in that earlier patent application, there are twelve such elements. Each element is discrete and is mounted in a groove formed in the circumference of a core member.
As explained in that earlier patent application, the degree of visual resolution obtainable depends upon the rate of signal output and resultant echo signal. This rate can be increased by increasing the number of transducer elements or alternatively by rotating a given number of transducer elements, as indicated in that earlier patent application.
There are clearly advantages and disadvantages associated with either attempting to increase the number of transducer elements in the case of a stationary transducer (i.e non-rotatable) and attempts to provide a drive arrangement for a rotatable transducer arrangement having fewer elements.
These difficulties are due to the very small scale involved in this type of transducer arrangement. Typically, the catheter at the end of which the transducer arrangement is mounted is less than 2.0 mm in diameter and typically 1.0 mm. It can thus be appreciated that the extremely small size of the transducer arrangement as a whole imposes limitations on the number of transducer elements which can be accommodated around the circumference. Equally, because of the very small scale involved, it is difficult to provide a rotatable transducer arrangement with an appropriate drive arrangement that can operate through tortuous vessels.
The present invention is concerned with improving the visual resolution referred to earlier by increasing the number of transducer elements beyond the maximum number which it had up to the present time been thought practicable in such a small scale arrangement.
SUMMARY OF THE PRESENT INVENTION
According to a first aspect of the present invention, in a transducer arrangement of the kind described, the transducer elements are formed from a single annulus, each transducer element being defined in relation to adjacent transducer elements by a physical discontinuity between adjacent elements to render each element separate from the other elements and the arrangement is characterised in that the transducer array has a diameter no greater than two millimetres and typically one millimetre and a number of discrete transducer elements not less than thirty-two and preferably not less than forty-eight and even more preferably not less than sixty-four.
The physical discontinuity could take the form of a slot which has been formed in the annulus by means of a laser beam, a grinding or sawing operation, a chemical etching operation or combination of these.
According to a second aspect of the present invention, the transducer array is manufactured from a single annulus of electrically polarised lead zirconate titanate (PZT), the individual transducer elements being defined by circumferentially spaced slots which. run substantially parallel to the axis of the annulus. The PZT may be electrically polarised before or after creation of the slots.
According to a third aspect of the present invention, the PZT cylindrical annulus is mounted on a tungsten carbide tube or other suitable rigid conducting tube to which it is bonded.
According to a fourth aspect of the p
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Barlow Christopher J.
Dickinson Robert J.
Nix Elvin L.
Ryan Patrick J.
Gunnison Forrest E.
Intravascular Research Limited
Jaworski Francis
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