A miniature transducer designed for use in a medical imaging system catheter probe is disclosed. The transducer has an electric cavity and coaxial construction for preventing electric fields from being emitted or received by the transducers. The construction of the transducer enables two to be mounted very close to one another on a thin catheter probe, one for transmitting acoustic pulses and the other for sensing echoes in response to the acoustic pulses, for imaging extremely close targets. The transducers can be secured to the catheter probe in such a way as to substantially acoustically isolate one from the other. A method of making the transducer by applying several electrically-conductive and insulating coatings and layers to a core in selected sequence so as to create a transducer having an electrical cavity, coaxial construction.
RELATED APPLICATIONS
This application is a divisional application of U.S. application, Ser. No. 151,394, filed Feb. 2,1988 and now U.S. Pat. No. 4,862,893, which in turn is continuation-in-part of co-pending application U.S. application Ser. No. 129,830 filed Dec. 8, 1987 in the names of Michael Martinelli and Peter von Thuna (hereinafter referred to as the "Parent Application") and now U.S. Pat. No. 4,821,731, the latter application being a continuation-in-part of U.S. application Ser. No. 856,621 filed Apr. 25, 1986 in the names of Michael Martinelli, Thomas Aretz, John Butterly and Stanley M. Shapshey, and now abandoned.
A medical probe such as a catheter comprises a flexible, elongated member having distal and proximal ends, with Doppler-type velocity measuring means carried within said probe adjacent said distal end, and electrical wires carried within the probe and communicating between the measuring means and the proximal probe end for connection to an electronic system for processing signals from the Doppler chip. By this invention, at least a portion of the probe, including the distal end and Doppler crystal has an ovoid cross-sectional shape. The portion has a maximum cross-sectional dimension and a minimum cross-sectional dimension substantially perpendicular thereto to provide lateral spaces for flow outside of the probe while the probe resides in a blood vessel.
An improved ultrasonic transducer for a catheter tip has a thin strip of piezoelectric polymer film formed into a spiral ring and adhesively mounted on the support structure near the catheter tip. Electrical connection between the back face of the film and the support structure negative electrode is via capacitive coupling. Connection to the front face of the film is via a wire connected to the positive electrode of the catheter. A further embodiment suitable for a needle transducer is formed by coating the tip with a solution of PVDF co-polymer to form the actual transducer.
Novel intravascular, ultrasonic imaging catheters are provided which utilize thin layers of a flexible plastic material, such as PVDF, which can be spot polarized in active regions which are to serve as piezoelectric transducers. Thin layer metallic electrodes are deposited on opposing surfaces of these active regions. Strips of the appropriately configured material also having shielding and backing and/or core forming portions are spiral wound into a completed catheter. Alternatively, the catheters are fabricated from extruded PVDF tubing which may be formed around a central core which carries those electrodes which are to contact the inner surface of the extruded tube.
In an ultrasonic probe for use in ultrasonic endoscope, ultrasonic diagnosing apparatus and other ultrasonic apparatuses, an ultrasonic vibrator is arranged in a recess formed in a cylindrical housing and is secured thereto such that portions of first and second electrodes are exposed out of the recess. First and second lead wires are embedded in the housing such that tips of the lead wires are exposed within connecting areas formed in the housing in communication with the recess. The tips of the first and second lead wires are connected to first and second electrodes of the ultrasonic vibrator with the aid of conductive members made of solder, conductive paste or conductive adhesive agent. The other end of the first and second lead wires are extended from the same end face of the cylindrical housing.
The present invention provides an improved drive shaft for use in a catheter system having a rotating imaging or interventional work element. A drive shaft according to the present invention is formed at least in part of a material having super elastic properties. This material provides an advantageous combination of column strength and torsional rigidity with the ability to sustain substantial bending without permanent deformation. Preferred embodiments are formed as hollow tubes to allow electrical conducting wires to be disposed within the body of the drive shaft. Some embodiments combine relatively rigid proximal segments with relatively flexible distal segments to allow for entry of the work element into narrow and twisting regions of a patient's vascular system.
