Guidewires with imaging capabilities have heretofore been provided as for example in U. S. Patent No. 5,558,093. Such guidewires have utilized an ultrasonic transducer assembly, at least a part of which must be rotated independent of rotation of the guidewire. The provision of such independent rotational capabilities has made it difficult to provide guidewires which have a sufficiently small diameter so that they can be readily used in small vessels as for example arterial vessels in the heart. There is therefore a need for a new and improved guidewire which overcomes these deficiencies.

In general, it is an object of the present invention to provide a guidewire having sidewise looking capabilities which can be utilized in manufacture of small diameter guidewires to permit use of the same in a method for treatment of stenoses in small vessels with over-the-wire catheters.

Another object of the invention is to provide a guidewire of the above character which has a small profile in cross- section from the proximal extremity to the distal extremity.

Another object of the invention is to provide a guidewire of the above character which has a flexible tip which can function in the same manner as the flexible tip of conventional guidewires and which can have the same feel as the flexible tips of conventional guidewires.

Another object of the invention is to provide a guidewire of the above character which can be economically manufactured.

Another object of the invention is to provide a guidewire of the above character which has gowd torque transmission while retaining flexibility and kink resistance.

Another object of the invention is to provide a guidewire of the above character in which more than one ultrasonic transducer is utilized.

Another object of the invention is to provide a guidewire of the above character in which a plurality of ultrasonic transducers are provided which are spaced apart circumferentially.

Another object of the invention is to provide a guidewire of the above character in which the transducers are spaced apart longitudinally.

Another object of the invention is to provide a guidewire of the above character in which the provision of the ultrasonic transducer in the guidewire does not substantially interfere with the flexibility and feel of the flexible tip of the guidewire.

Additional objects and features of the invention will appear from the following description in which the preferred embodiments are set forth in detail in conjunction with the accompanying drawings.

Figure 1 is a side elevational view of a guidewire incorporating the present invention coupled into a conventional computer and ultrasonic power supply and receiver.

Figure 2 is a cross-sectional view taken along a line 2-2 of Figure 1.

Figure 3 is an enlarged cross-sectional view of the distal extremity of the guidewire shown in Figure 1.

Figure 4 is a cross-sectional view of the distal extremity of another embodiment of a guidewire incorporating the present invention.

Figure 5 is a cross-sectional view of the distal extremity of still another embodiment of a guidewire of the present invention.

Figure 6 is a cross-sectional view taken along the line 6-6 of Figure 5.

Figure 7 is a cross-sectional view taken along the line 7-7 of Figure 5.

In general, a guidewire is provided which has sidewise ultrasonic imaging capabilities for deployment across a complex lesion in a vessel formed by a wall and normally having a lumen extending therethrough and for use with over-the-wire catheters.

A flexible elongate tubular member is provided which has proximal and distal extremities and has a lumen extending from the proximal extremity to the distal extremity. Means is carried by the proximal extremity of the flexible elongate tubular member adapted to be grasped by the human hand for rotating the flexible elongate tubular member. A sidewise looking ultrasonic transducer is carried by the distal extremity of the flexible elongate tubular member and is mounted thereon for rotational movement therewith as the guidewire is rotated.

Electrical conductors are provided within the lumen of the flexible elongate tubular member and are utilized for supplying electrical energy to the ultrasonic transducer and for receiving electrical energy from the ultrasonic transducer. A flexible coil is secured to the distal extremity of the flexible elongate tubular member.

More in particular as shown in Figure 1 of the drawings, the sidewise looking ultrasonic imaging guidewire 11 of the present invention is coupled to an ultrasonic power supply 16 which has associated therewith a notebook or laptop computer 17 of a conventional type which is provided with a keyboard 18 and a screen 19 in the form of an LCD panel. The proximal extremity of the guidewire 11 is coupled into the ultrasonic power supply 16 and the computer 17 through a coupling assembly 21 through an electrical cable 22 to a conventional shaft encoder 23 mounted in the ultrasonic power supply 16 and the computer 17.

The guidewire 11 consists of a flexible elongate tubular member 26 having proximal and distal extremities 27 and 28 and having a lumen 29 extending therethrough from the proximal

extremity 27 to the distal extremity 28. The flexible elongate tubular member 26 can have a suitable length as for example 175 cm and can have a diameter ranging from 0.010"to 0.032" and preferably a diameter of 0.012"to 0.014". In accordance with the present invention the flexible elongate tubular member 26 is formed of a material having high torsion capabilities so as to obtain substantially one-to-one correspondence between rotation of the proximal extremity and the distal extremity. In this connection, it has been found that stainless steel as for example 302 stainless tubing often called"hypotube"forms a very satisfactory product for this purpose. The wall thickness of the stainless steel tube should be at least 1 mil and preferably approximately 2 mils so that for a 0.014"outside diameter hypotube, the lumen 29 therein would have a diameter of 0.010"to provide adequate space for electrical conductors as hereinafter described.

A transducer assembly 36 is carried by the distal extremity of the flexible elongate tubular member 26 and consists of a cylindrical housing 37 which has an outside diameter substantially the same as the outside diameter of the flexible elongate tubular member 26. The housing 37 is provided with ends 38 and 39 of reduced diameter. End 38 is fitted within the lumen 29 of the distal extremity 28 of the flexible elongate tubular member 26 and is secured therein by suitable means such as solder 41. A high efficiency piezoelectric transducer element 46 is mounted within the cylindrical housing 37 in a fixed position so that it rotates as the housing 37 is rotated by rotation of the flexible elongate tubular member 26. The transducer element 46 is formed of a PZT material of a conventional type and has a generally rectangular configuration.

By way of example it can have a thickness of. 002" and can have a width of. 011" and a length of. 020". Thus the transducer element 46 is provided with spaced apart planar opposite surfaces 47 and 48. The transducer element 46 can be designed

to operate at a frequency ranging from 10 to 100 MHz and preferably within a range of 36 MHz to 90 MHz and still more preferably at a frequency ranging from 40 to 60 MHz.

An insulating sleeve 51 is provided and is formed of a suitable material such as a polyimide. The polyimide insulating sleeve 51 is provided with a rectangular window 52 which has a size which is substantially greater than the size of the surface 47 of the transducer element 46. This window 52 is in registration with a window 53 provided in the housing 37.

First and second insulated conductors 56 and 57 are provided in the form of a twisted pair extending through the lumen 29 from the proximal extremity 27 to the distal extremity 28. Means is provided for forming a connection between the first and second conductors 56 and 57 and the front and back sides or surfaces 47 and 48 of the transducer element 46 as shown particularly in Figure 3. The first conductor 56 has a bare hook-shaped end 58 disposed within a conductive epoxy 61 of a suitable type as for example a silver-filled epoxy which is placed in the polyimide sleeve 51 to form a bed for supporting the transducer element 46 in a position generally centrally disposed within the insulating sleeve 51. After the transducer element 46 has been seated so that its surface 48 is in intimate contact with the conductive epoxy 61, an insulating epoxy 62 is then formed around the side edges of the transducer element 46 and also to cover the conductive epoxy 61. A conducting layer 63 formed of a suitable material such as sputtered gold overlies the insulation 62 and makes intimate contact with the top surface 47 of the transducer element 46. The gold sputtered conducting layer 63 can be formed to a suitable thickness as for example 2000 A. The bared end 64 of the conductor 57 is bonded to the conducting layer 63 in a suitable manner such as by solder 66. The remaining space within the insulating sleeve 51 overlying the conductive layer 63 is filled with a suitable acoustic impedance matching encapsulant 67 to serve as an

impedance matching layer for matching the impedance of the surface 47 to ambient as for example in blood. The acoustic matching layer 67 typically has a thickness corresponding to one-quarter wavelength of the acoustical signal passing therethrough. It should be appreciated that if desired a lens formed of the same material can be provided in place of the acoustic matching encapsulant 67 which in addition to providing impedance matching can actually focus the beam to a wider or narrower beam.

A floppy tip 71 is provided as a part of the guidewire 11 which has generally the same feel and characteristics of a conventional floppy guidewire, for example the high torque floppy manufactured and sold by Guidant Corporation. This floppy tip consists of a core wire 72 formed of a suitable material such as stainless steel, platinum or Nitinol as a proximal extremity 73 of a slightly reduced diameter which is secured in the distal end 39 of the housing 37 by a suitable means such as solder 74.

The floppy tip 71 can have a suitable length ranging from 2 to 25 cm and preferably has a length ranging from 5 cm to 20 cm. Depending on the selected length of the floppy tip 71, the core wire 72 must have corresponding dimensions and as hereinbefore explained is provided with a proximal portion 72a of reduced diameter. From this portion of reduced diameter, there is provided an elongate cylindrical portion 72b which generally corresponds to the selected length of the floppy tip 71. Proceeding in a distal direction, the core wire 72 is provided with a tapered portion 72c and a flattened portion 72d.

A coil 76 is provided preferably formed of a radiopaque material such as a platinum-tungsten alloy or stainless steel formed from a wire having a suitable diameter as for example 0.003" and formed into turns to provide the coil 76 with the proximal end of the coil 76 being secured over the end 39 of the housing 37 by suitable means such as solder 77. The other or

distal end of the coil 76 is secured to the distal extremity of the flattened portion 72d by a hemispherical ball of solder 78.

In order to substantially increase the kink resistance of the flexible elongate tubular member 26, the lumen 29 therein can be filled with a filler 81 of a suitable material such as a liquid epoxy or resin and permitted to harden. Alternatively, a polymer can be utilized in powder form and can be melt formed therein. Thus it can be seen that the filler 81 fills the void within the lumen and greatly reduces the possibility of kinking of the hypotube forming the flexible elongate tubular member 26.

Means is provided for rotating the proximal extremity of the flexible elongate member and consists of a conventional torquer 86 which is mounted on the proximal extremity 27 of the flexible elongate tubular member 26. As is well known to those skilled in the art, the torquer 86 is provided with a pin vise so that it adapted to frictionally engage the proximal extremity 27 so that as the torquer 86 is rotated by the hand of the physician grasping the same, the flexible elongate tubular member 26 will also be rotated.

Operation and use of the guidewire of the present invention may now be briefly described in conjunction with the method of the present invention. The guidewire 11 as supplied by the manufacturer is taken from its packaging by the physician. The torquer 86 is mounted on the proximal extremity. The proximal extremity is then connected through the connector assembly 21 to an electrical cable 22 that is connected to the power supply 16 and the computer 17. As soon as this has been accomplished, ultrasonic power is supplied to the conductors 56 and 57 to the transducer element 46 to cause it to emit ultrasonic energy at the selected frequency. The transducer element 46 would also respond to ultrasonic or returning echo signals reflected which would be supplied to the conductors to the power supply. The analog signal received is amplified and filtered in a conventional manner and thereafter converted into a digital

signal which is supplied to the computer 17. The computer 17 converts the linear array of vectors received from the transducer element to a circular array of vectors which would be displayed on the screen 19 to show the wall structures being impinged upon by the ultrasonic energy emitted from the transducer element 46 as it rotates in the vessel.

Let it be assumed that it is desired to treat a stenosis in a vessel of the heart. Access is obtained through the femoral artery. The flexible floppy tip 71 of the guidewire is fashioned in a conventional manner by the surgeon and then introduced into the opening through the femoral artery and the guidewire is then advanced in a conventional manner in the vessel until the stenosis is reached. During the time that the guidewire 11 is being advanced, the torquer 86 can be operated by the physician to torque the guidewire 11 as desired while the physician watches the image appearing on the screen 19 to ascertain what is being viewed by the sidewise looking transducer element 46.

The physician by operating the torquer 86 can rotate the guidewire anywhere from 0 to 49 revolutions or in other words 49 revolutions or less per minute and preferably from 10 to 25 revolutions per minute. It has been found that revolutions at this speed are adequate for the physician to view the wall structure being examined by the sidewise looking transducer element 46. At the same time that the ultrasonic images are being displayed on the screen 19, the advancement of the distal extremity 28 of the flexible elongate tubular member 26 can be viewed fluoroscopically in a manner well known to those skilled in the art. The sector being displayed on the screen 19 can be as little as 5° but typically can range from 12° to 15°. As the guidewire is being rotated by movement of the torquer 86, each successive segment displayed on the screen 19 will improve the signal quality of the previous segment so that there is a natural averaging as the segments are progressively displayed on

the screen 19 during rotation of the torquer 86 through successive revolutions.

As soon as it has been ascertained that the guidewire has been advanced to the desired location with respect to the stenosis as for example in a position advancing through the stenosis, a therapeutic device such as a balloon catheter or a stent delivery catheter is advanced over the guidewire 11 until the image being displayed on the screen 19 shows that the therapeutic catheter has been moved over the transducer element 46. In this way, it is possible for the physician to precisely position the therapeutic device in the stenosis to be treated.

Thereafter, the balloon on the balloon dilatation catheter can be inflated to enlarge the flow passage through the stenosis in a conventional manner. If a still further enlargement is desired within the stenosis, the balloon catheter can be removed and another larger balloon catheter inserted over the guidewire and positioned in a similar manner and thereafter operated to create a still larger opening through the stenosis in the vessel. In the same manner, a stent delivery catheter can be advanced over the guidewire if that type of therapeutic device is desired.

After the desired therapeutic procedures have been carried out, the therapeutic catheters and the guidewire 11 can be removed in a conventional manner and the opening in the femoral artery closed in a conventional manner.

It should be appreciated that since the cylindrical housing 37 has a relatively short length ranging from for example 2 mm to 8 mm, the transducer assembly 36 can be disposed in various locations with respect to the floppy tip 71 since it is proximal of the floppy tip 71 as shown in Figures 1,2 and 3. Thus as shown in Figure 4, to provide a longer floppy tip 71 an intermediate section 91 has been provided which can have a length ranging from 5 to 20 cm and greater. This intermediate section 91 consists of a braided tubular body 92 in a length

corresponding to the length of the intermediate section 91 formed in a conventional manner. For example it can be formed by utilizing braided stainless steel flat ribbon into which a suitable plastic has been extruded to form a tubular member having an outside diameter corresponding to the outside diameter of the flexible elongate tubular member 26 and having a similar wall thickness to provide a lumen 93 extending therethrough.

A proximal core wire 96 has been provided which as shown has its proximal extremity 97 secured in the distal extremity 28 of the flexible elongate tubular member 26 by suitable means such as solder 98. This proximal core wire 96 is tapered throughout its length and has the first and second conductors 56 and 57 wound thereon and making connection to the transducer element 46 in the manner hereinbefore described in conjunction with Figures 1 through 3.

Operation and use of this embodiment of the guidewire as shown in Figure 4 is very similar to that hereinbefore described with the embodiment shown in Figures 1 through 3. The principal difference is that there has been provided a guidewire 89 which has a longer flexible floppy tip when that is desirable. The outer surface of the braided tubular body 92 can be provided with a lubricious coating (not shown) if desired.

From the construction shown in Figure 4 it also can be seen that the transducer assembly 36 because of its small size can be incorporated into the coil 76 itself by merely pulling apart the turns making the coil to provide a sufficient space between two turns of the coil and then separating the core wire into two components and soldering the ends of the housing 37 to the opposite ends of the core wire. In this way, a construction similar to that shown in Figure 4 has been provided with the exception that the transducer assembly 36 has been provided within the length of the coil 76. The operation and use of such an embodiment would be very similar to that hereinbefore described with respect to the previous embodiments.

WHAT IS CLAIMED: 1. A guidewire having sidewise ultrasonic imaging capabilities for deployment across a complex lesion in a vessel formed by a wall comprising a flexible elongate tubular member having proximal and distal extremities and having a lumen extending from the proximal extremity to the distal extremity, a sidewise looking imaging element carried by the distal extremity of the flexible elongate tubular member and mounted for rotational movement with the proximal extremity of the flexible elongate tubular member as the proximal extremity is rotated, means supplying energy to the imaging element and extending to the proximal extremity and a flexible coil secured to the distal extremity of the flexible elongate tubular member to provide a floppy tip.

2. A guidewire as in Claim 1 wherein said flexible elongate tubular member has a substantially uniform diameter throughout its length so that the guidewire can serve as a guidewire for deployment of therapeutic catheters thereon.

3. A guidewire as in Claim 1 wherein said imaging element is an ultrasonic transducer mounted in a cylindrical housing so that it can transmit and receive ultrasonic energy through the window.

4. A guidewire as in Claim 3 further including acoustic matching means mounted in the window.

5. A guidewire as in Claim 3 wherein said floppy tip is secured to the housing and consists of a tapered guidewire secured to the housing and a coil of radiopaque material extending over the core wire and secured to the housing and to the distal extremity of the core wire.

Still another embodiment of the invention is shown in Figures 5,6 and 7 showing transducer elements spaced apart longitudinally and circumferentially of the distal extremity of the guidewire. Thus as shown particular in Figures 5,6 and 7, a guidewire 101 having a distal extremity 102 has four of the transducer elements 46 which are spaced 90° apart and have the surfaces 47 facing windows 103 provided in an insulating sleeve 104 and windows 106 extending through a flexible elongate tubular member 107. The transducer elements 46 are mounted within the insulating sleeve 104 in a manner similar to that hereinbefore described and are sitting on a pad 111 of a conducting epoxy to which an insulated conductor 112 extends with all four of the insulated conductors 112 being interconnected into a single conductor 113 and returned thereby to the proximal extremity of the flexible elongate tubular member 107. The surfaces 47 of the transducer elements 46 are each connected to separate insulated conductors 116-119 respectively by the use of solder and a sputtered gold coating in the manner hereinbefore described. Matching layers 121 of the type hereinbefore described such as made of Tacon can be provided for the transducer elements 46.

The flexible elongate tubular member 107 consists of a stainless steel core wire 126 which has a tapered distal extremity 126a which has wound thereon a multiple conductive cable 127 having typical dimensions of 0.001" x 0.005" and having at least five conductors thereon connected to the conductors 113 and 116-119. The cable 127 can be what is typically called a multifiler cable and can be provided with conductors which are round or rectangular in cross section.

Shrink tubing 128 of a polyester covers the wound multiple conductive cable 127. A plastic encapsulated braided jacket 129 covers the shrink tubing 128 and can use stainless steel wire of suitable dimensions such as 0.0005" x 0.0025". A hydrophilic coating 131 overlies the jacket 129.