WO1996033754A1

WO1996033754A1 - Imaging catheter with no-fill sheath

Info

Publication number: WO1996033754A1
Application number: PCT/US1996/005613
Authority: WO
Inventors: Robert J. Crowley
Original assignee: Boston Scientific Corporation
Priority date: 1995-04-24
Filing date: 1996-04-22
Publication date: 1996-10-31
Also published as: AU5566096A

Abstract

A catheter for diagnosing body interiors utilizing the transmission and receiving of ultrasonic waves. The catheter has a patient insertable distal end (16) and a proximal end (20) and comprises an elongated catheter sheath including an ultrasonically transmissible section (13) adjacent the distal end. It further includes a reservoir disposed within the sheath and adjacent the distal end. A frangible membrane (15) is disposed within the sheath and seals the reservoir from the interior of the sheath. A liquid (12) is disposed within the reservoir and contained therein by the frangible membrane. A transducer (11) for generating and receiving the ultrasonic waves is used to break the membrane when it is slipped into the sheath so the transducer will be bathed in the liquid and provide sonic transmissions within the catheter.

Description

IMAGING CATHETER WITH NO-FILL SHEATH

Field of the Invention

The present invention relates to a sheath for an imag¬ ing catheter with a means to retain fluids for use with ultrasonic imaging catheters and other catheters or guide- wires which require a fluid contact for operation. Ultra- sonic imaging catheters are used for internally viewing body portions with ultrasonic waves generated by a generator/receiver disposed within the catheter. Such catheters involve the transmission and reception of ultra¬ sonic waves through the catheter's walls and especially through a "window" after the catheter has been worked into various body conduits. Such ultrasonic catheters require a wave transmission fluid in the catheter between the trans¬ mitter, the receiver and the body part being examined.

Description of the Prior Art

Filling a catheter with a liquid to provide for low acoustic attenuation can be fairly difficult and time con¬ suming. One way that has been used is to fill the catheter from its proximal end with a ultrasonic transmission fluid. Such methods, however, can entrap a bubble at the closed distal end of the catheter. Bubble formation is likely because of the narrow passageway within the catheter. A bubble in the wrong place may completely spoil any image generated by the imaging catheter. As an alternative to filling the catheter from the proximal end, the United States Patent to Crowley et al., number 5,002,059, discloses a disposable catheter which is formed from an acoustically transparent resilient flexible material in which the distal end of the catheter sheath is arranged to receive a septum thereon. The septum can be a cylindrically-shaped plug which can receive a needle-tipped syringe that is filled with an acoustically transmitting fluid. While such mechanisms for filling the catheter with transmission fluid have proven successful, I have found that the use of a hypodermic needle to inject the fluids can be eliminated through the use of the acoustic septum and window of the present invention. The United States Patent to Sieben et al., 5,243,988, also discloses an ultrasonic imaging device where the fluid is introduced into the proxi¬ mal end of the catheter and excess fluid is poured out from the proximal end after the catheter is filled. The United States patent to Crowley, No. 5,400,785, discloses a fluid permeable film on the end of the catheter that allows the flow of a liquid into the catheter from a source. When the catheter is full, a coating on the film swells and prevents the flow of liquids in either direction whereby the opera¬ tional liquids are entrapped within the catheter.

Summary of the Invention The present invention relates to a catheter for diag¬ nosing body interiors utilizing the transmission and recep¬ tion of ultrasonic waves. The catheter has a patient insertable distal end and a proximal end. It includes an elongated catheter sheath with a section that is transmissi¬ ble of ultrasonic waves. A reservoir is disposed within the sheath and adjacent the distal end. A frangible membrane formed of a conventional polymeric material such as silicone rubber, polyethylene or wax (paraffin) is disposed within the sheath and serves to seal the reservoir from the interi¬ or of the sheath. The membrane preferably has a thickness between about 0.1 and 0.5 mm. A liquid is disposed within the reservoir and contained therein by the membrane. When the membrane is broken the liquid in the reservoir is used to bathe the ultrasonic wave generating and receiving device and provide for sonic coupling and transmission within the catheter so a signal can be generated and subsequently displayed of the body organ being viewed with the catheter. In the preferred embodiment, the ultrasonic generating and receiving device is a transducer and this transducer is used to break the membrane and provide for bathing of the trans¬ ducer in the liquid in the reservoir. The ultrasonic gener¬ ator and receiver is in electrical communication with a signal generating and receiving device for displaying data that is generated within the catheter.

Brief Description of the Drawings Figures 1, 2 and 3 are side elevational views, partial¬ ly in cross-section, showing, stepwise, introducing a rotat- able ultrasound generating and receiving device into a catheter sheath, puncturing a membrane to enter a reservoir of liquid and lastly, bathing the device in the liquid whereby to provide for sonic coupling between the body part being examined and the ultrasonic generating and receiving device.

Description of the Preferred Embodiments Referring now to Figure 1 there is shown an exploded view of an ultrasound imaging catheter device 10 which utilizes a rotatable and slidably insertable ultrasound generating and receiving means 11 and flexible catheter sheath 14 having a distal end 16 forming an acoustic window 13. Preferably, the acoustic window 13 comprises the entire distal end of the catheter sheath 14 and can be integral with the catheter sheath 14 and formed of the same material or can be of a different material and molded to the end of the catheter sheath. A liquid filled reservoir 12 is disposed in the distal end of the catheter sheath 14. The liquid, commonly sterile water or saline, is used as an acoustic coupler between the organ being catheterized and the generating and receiving means 11. A membrane 15 is disposed within the sheath 14 and forms a frangible cover for the reservoir 12.

In this view the image generating and receiving means 11 comprises a single transducer element directed at an angle to the axis of a drive shaft 9. In Figure 1 the tip 11a of the transducer 11 is shown disposed adjacent the membrane 15 and prior to puncturing it so that the liquid in the reservoir 12 remains therein. Essentially, the view shows the insertion of the transducer 11 into the catheter sheath immediately prior to the tip 11a engaging the mem¬ brane 15.

In Figure 2, the tip 11a is shown engaging the membrane 15 to break it. When broken, as shown in Figure 3, the volume of the tip 11 and the drive shaft 9 will cause the liquid in the reservoir 12 to fill the sheath 14. The size of the reservoir 12 is not critical so long as it contains sufficient liquid to fully enclose the transduc¬ er 11 and the drive shaft 9. If there is more liquid in the reservoir 12 than is needed to fill the sheath 14 when the transducer 11 and the shaft 9 are inserted, the liquid will merely flow out of the proximal end of the sheath 14 and can be discarded.

As shown in Figure 3 the catheter sheath 14 is filled with liquid and bathes both the transducer 11 and the drive shaft 9. A conventional means (not shown) is provided for rotating the shaft 9 at a speed in the order of 1800 rpm. To control emission in excess of 10 megahertz, a convention¬ al position detecting means (not shown) is disposed at the proximal end of the drive shaft 9 for detecting the instan- taneous angular position of the shaft 9 to represent the instantaneous angle position of the transducer 11. A TV monitor (not shown) which is responsive to return signals from the transducer and to the position detecting means provides a display of the acoustical image based on the signals detected by the transducer.

The catheter 10 preferably uses a drive shaft 9 having an outer diameter through its length of about 1 mm or less. The sheath 14 surrounds the distal end of the drive shaft 9 and is adapted to provide dynamic viscous drag to the shaft during its rotation to enhance the mechanical ability of the angular displacement between the proximal and distal ends of the catheter. The difference between the outer diameter of the shaft 9 and the inner diameter of the corresponding portion of the sheath 14 is in the range of about 0.05 to 0.15 mm. The acoustic window 13 is substantially transpar- ent to acoustical energy transmitted and received by the transducer 11. The drive shaft 9 can have a liquid pumping screw form contour whereby the drive shaft 9 is exposed to liquid in the sheath and is driven in the direction tending to decrease the diameter of the outer coil. The outer surface of the coil is effective to pressurize liquid dis- tally thereof. There is fluid communication between the liquid fluid space along the drive shaft 9 and the space occupied by the transducer 11, that is area which formerly constituted the reservoir 12. The proximal end 20 of the catheter is of conventional construction, as is well to the art.

It is apparent that modifications and changes may be made within the spirit and scope of the present invention. It is my intention, however, only to be limited by the following claims.

As my invention, I claim.

Claims

1. A catheter for diagnosing body interiors utilizing the transmission and receiving of ultrasonic waves, said catheter having a patient insertable distal end and a proxi¬ mal end, said catheter comprising: an elongated catheter sheath including an ultrasonical- ly transmissible section adjacent said distal end; a reservoir disposed within said sheath and adjacent said distal end; frangible means disposed within said sheath sealing said reservoir from the interior of said sheath; a liquid disposed within said reservoir and contained therein by said frangible means; means to break said frangible means to enable a device for generating and receiving ultrasonic waves to be bathed in said liquid and provide sonic transmissions within said catheter.

2. The catheter according to claim 1 wherein said frangible means is a membrane of polymeric material.

3. The catheter according to claim 2 wherein the polymeric material is a member selected from the group consisting of polyethylenes and paraffins.

4. The catheter according to claim 1 wherein the membrane has a thickness between about 0.1 and 0.5 mm.

5. A catheter for diagnosing body interiors utilizing the transmission and receiving of ultrasonic waves generated therewith, said catheter having a patient insertable distal end and a proximal end, said catheter comprising: an elongated catheter sheath including an ultrasonical- ly transmissible section adjacent said distal end; a reservoir disposed within said sheath and adjacent said distal end; frangible means disposed within said sheath sealing said reservoir from the interior of said sheath; a liquid disposed within said reservoir and contained therein by said frangible means; means for generating and receiving ultrasonic waves adapted to be disposed within the distal end of said cathe- ter and to extend from said proximal end to said distal end, said generating and receiving means constituting a means to break said frangible means to enable said means for generat¬ ing and receiving ultrasonic waves to enter said reservoir and be bathed in said liquid and provide ultrasonic trans- missions within said catheter.