EP0576607A4 - Catheter for laser treatment of atherosclerotic plaque and other tissue abnormalities - Google Patents

Abstract

A medical catheter (10) for treating atherosclerotic plaque (16) and other abnormalities includes optical fibers (30) for applying laser energy to the plaque (16) and an ultrasonic transducer system (32, 34) for sensing the location and configuration of the plaque (16). The optical fibers (30) and electrical wiring (40) for the transducers (32, 34) extend through a probe (28) which is rotatable inside of the catheter tube (12) to provide universal directional control of the fibers (30) and transducers (32, 34). A reflective system includes a curved reflector (38) in the probe (28) which can be axially adjusted to vary the directions of the ultrasonic signals. Alternative forms of the invention include different reflector schemes, an angled ultrasonic transducer (32, 34) having a conical signal output that varies with frequency, and various different systems for rotating the transducers (32, 34) and fibers (30).

Description

V

CATHETER FOR LASER TREATMENT OF ATHEROSCT.T^gTtrrTTr PLAQUE AND OTHER TISSUE ABNORMALITIES

This invention is a continuation in part of patent appli¬ cation serial no. 470,722, filed on January 26, 1990 in the name of Thomas R. Winston for "APPARATUS FOR PHOTOA- BLATIVE TREATMENT OF ATHEROSCLEROTIC LESIONS".

5

This invention relates generally to the medical use of laser energy and deals more particularly with a catheter which is equipped with optical fibers for the transmis¬ sion of laser energy and also with an ultrasonic trans-

10 ducer system for sensing the character and configuration of the area that is to be medically treated by the laser energy.

It has long been known that cardiovascular problems are 15 caused by the presence of atherosclerotic plague on the walls of veins and arteries, especially coronary arter¬ ies. For some time, there has been interest in the use of laser energy to remove plague and to treat abnormali¬ ties on internal organs in the body. Typically, it is 20 proposed to use a catheter that contains optical fibers for transmitting the laser energy through the catheter to the area that is to undergo treatment. Lasers have also been used to treat other medical problems such as tumors or other abnormalities in the colon, esophagus, prostrate 25 and other areas of the body. U.S. Patent No. 4,576,177 to Webster discloses a catheter which includes optical fibers in combination with an ultrasonic transducer having the capability of transmit¬ ting and receiving ultrasonic signals. The reflections of the ultrasonic signals from the tissue are received by the transducer to provide information as to the character and configuration of the tissues so that the laser energy can be applied properly to the plaque lesion and not to unoccluded artery walls or other healthy tissues.

In the device disclosed in the Webster patent, the ultra¬ sonic transducer takes the form of a flat ring which is oriented at an angle to the axis of the catheter. With this arrangement, it is necessary to rotate the catheter through a full 360° circle in order to direct the ultra¬ sound at the entire circumference of the artery. The need to manually rotate the catheter is at best a severe inconvenience and an inaccurate procedure because the catheter cannot be accurately stepped through incremental arcs in order to provide a reliable profile of the arte¬ rial plaque. If the ultrasound techniques are inadequate to provide the instrument with an accurate configuration of the plaque, the laser energy can be misdirected such that it is not only ineffective in treating the problem but also possibly destructive of healthy tissues.

The present invention is an improvement over the catheter described in the previously mentioned Webster patent and is directed primarily at providing an ultrasonic system that is improved in its accuracy, practicality and reli¬ ability.

In accordance with the invention, a catheter equipped with an optical fiber for transmitting laser energy is also provided with an ultrasonic sensing system that is able to accurately determine the character and configura¬ tion of the entirety of an artery wall or other treatment area without the need for manual turning of the catheter. In one form of the invention, the ultrasound system is carried by a probe that extends through the catheter and may be rotated inside of the catheter by a stepping motor or the like in order to sweep the ultrasonic sensing system through 360° in selected increments. As a result, accurate information can be obtained as to the profile of an occlusion or other abnormality. One ultrasonic trans¬ ducer can be oriented radially to sweep around the entire circumference of the artery as the probe is rotated. In many cases, it is desirable to provide a second ultrason- ic transducer which is oriented to direct ultrasonic signals forwardly, either parallel to the catheter axis or at a slight angle to it to sense the artery geometry ahead of the probe.

The invention is particularly characterized in one of its forms by a concave reflector which directs the ultrasonic signal forwardly from the second transducer. The reflec¬ tor can be axially adjusted in order to vary the angle of the reflected signal relative to the catheter axis. This permits the tissue profile ahead of the probe to be determined accurately and at different locations along the artery. The adjustment of the reflector can be carried out in a variety of different ways, and the probe itself can be adjusted axially for even more versatility of the instrument.

In another form of the invention, the probe is stationary relative to the catheter but is equipped with a number of optical fibers which are arranged in a circular pattern around the circumference of the probe. A conical mirror on the tip of the probe directs the laser energy from each fiber in a radial direction so that all areas around the circumference of the probe can be treated without need for rotation of the catheter or probe. A phased array of ultrasonic transducers transmits radial ultra¬ sonic signals and permits the configuration of the artery wall around its entire circumference to be sensed without rotation of the catheter or probe. A

Still another form of the invention includes a probe through which the optical fibers extend and a smaller tube located within the probe and housing an ultrasonic transducer. The probe is rotatable within the catheter, and the smaller tube is itself rotatable within the probe. The optical fibers are arranged so that those having their inner ends closest to the center of the catheter have their outer ends farthest from the center. Consequently, when a shutter which controls the applica- tion of laser energy to the fibers is progressively closed, the fibers whose inner ends are closest to the center are deenergized first and the areas nearest the artery walls are treated last.

Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.

In the accompanying drawings which form a part of the specification and are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:

Fig. 1 is a fragmentary side elevational view of a cathe- ter constructed according to one embodiment of the present invention, with portions shown in section for illustrative purposes and the break lines indicating continuous length;

Fig. 2 is a fragmentary sectional view on an enlarged scale taken generally along line 2-2 of Fig. 1 in the direction of the arrows;

Fig. 3 is a fragmentary sectional view of the outer end portion of the probe for the catheter, showing a control wire and actuator for adjusting a mirror included in the tip end of the probe; Fig. 4 is a fragmentary sectional view on an enlarged scale of the tip ends of the probe and catheter;

Fig. 5 is a fragmentary sectional view similar to Fig. 4, but showing the mirror adjusted toward the tip of the probe from the position shown in Fig. 4;

Fig. 6 is a fragmentary sectional view showing the actua¬ tor for the control wire of the mirror;

Fig. 7 is a fragmentary sectional view on an enlarged scale taken generally along line 7-7 of Fig. 5 in the direction of the arrows;

Fig. 8 is a fragmentary side elevational view showing a catheter equipped with a cam drive system for adjusting the mirror in accordance with an alternative embodiment of the invention;

Fig. 9 is a fragmentary sectional view on an enlarged scale showing the cam drive system for the mirror;

Fig. 10 is a fragmentary side elevational view showing a drive system for axial adjustment of the probe within the catheter;

Fig. 11 is a fragmentary sectional view taken generally along line 11-11 of Fig. 10 in the direction of the arrows;

Fig. 12 is a fragmentary sectional view of the tip end of a catheter and probe constructed according to an alterna¬ tive embodiment of the invention;

Fig. 12a is a fragmentary sectional view of the tip end of a catheter and probe constructed according to another alternative embodiment of the invention; Fig. 13 is a fragmentary sectional view of the tip end of yet another alternative catheter and probe constructed according to the invention;

Fig. 14 is a fragmentary sectional view on an enlarged scale taken generally along line 14-14 of Fig. 13 in the direction of the arrows;

Fig. 15 is a fragmentary elevational view, partially in section, showing the tip end of yet another alternative catheter constructed according to the invention;

Fig. 16 is a block diagram of the electronic system used to excite the ultrasonic transducer of the catheter;

Fig. 17 is a.fragmentary sectional view of the tip end of still another alternative catheter constructed according to the invention;

Fig. 18 is a fragmentary end elevational view on an enlarged scale taken generally along line 18-18 of Fig. 17 in the direction of the arrows;

Fig. 19 is a fragmentary side elevational view, partially in section, showing still another alternative catheter constructed according to the invention;

Fig. 20 is a fragmentary end elevational view taken generally along line 20-20 of Fig. 19 in the direction of the arrows, with the shutter which controls the applica¬ tion of laser energy to the optical fibers partially closed;

Fig. 21 is an end elevational view similar to Fig. 20, but showing the shutter in the fully open position;

Fig. 22 is a fragmentary sectional view taken generally along line 22-22 of Fig. 19 in the direction of the arrows; Fig. 23 is a fragmentary sectional view taken generally along line 23-23 of Fig. 22 in the direction of the arrows;

Fig. 24 is a fragmentary elevational view of yet another alternative catheter constructed according to the inven¬ tion;

Fig. 25 is a fragmentary end elevational view on an enlarged scale taken generally along line 25-25 of Fig. 24 in the direction of the arrows; and

Fig. 26 is a diagrammatic view of the path traced by the ultrasonic transducer shown in Fig. 22 as the probe and transducer tube are rotated.

Referring now to the drawings in more detail and initial¬ ly to Fig. 1, numeral 10 generally designates a catheter which is constructed according to a first embodiment of the present invention. The catheter 10 includes a hollow- catheter tube 12 having an elongated configuration and a circular cross section. The catheter tube 12 has a size and construction to be inserted into the body to the area which is to undergo treatment. For example, if the catheter tube 12 is to be used for the treatment of atherosclerotic plaque, it should be small enough to be inserted into an artery such as the artery 14 which is plagued by the presence of plaque 16 on the interior of the artery wall. An annular balloon seal 18 may be provided on the inner end 12a of the catheter tube in order to provide a seal against the artery wall.

The opposite or outer end of the catheter tube 12 is designated by numeral 12b in Fig. 1 and may be secured to a stationary motor 20 which is preferably an electrical stepping motor. Referring additionally to Fig. 2, the motor 20 rotates an output shaft 22. A lined sleeve 24 fits within the^' output shaft 22 of the motor and is provided with a plurality of splines 26 that interfit with internal key ways 27 on the shaft 22. Consequently, the sleeve 24 is rotated directly with the shaft 22 but is able to slide axially relative to shaft 22 by reason of the sliding movement that is permitted of the splines 26 within the key ways 27 which receive them.

Sleeve 24 is fitted on and rigidly fixed to an elongated tubular probe 28 which extends through the length of the catheter tube 12 and is coaxial with it. The probe 28 is smaller in diameter than the catheter tube 12 and has an outer end to which sleeve 24 is fixed and an inner end 28a which projects out of the inner end 12a of the catheter tube. An optical fiber 30 extends through substantially the entire length of the probe 28, with the free end of the fiber 30 terminating within the inner end 28a of the probe. The optical fiber 30 extends substantially along the longitudinal axis of the probe and catheter tube and receives and transmits energy from a conventional medical laser (not shown) .

Referring additionally to Figs. 4-7, the tip end 28a of probe 28 is provided with a pair of conventional ultra¬ sonic transducers 32 and 34 which are mounted inside of the probe 28. the transducers 32 and 34 may be excited electrically in order to transmit ultrasonic signals, and the transducers also receive pulse echoes which are reflections of the transmitted signals. The received pulse echoes are transformed by the transducers into electrical signals to provide information as to the configuration and character of the tissues from which the signals are reflected. The transducers are preferably piezoelectric ceramic crystals.

The first transducer 32 is oriented to transmit a signal 32a (See fig. 4) which is directed radially out¬ wardly of the catheter and probe through a window 36 in the wall of the probe 28. The second transducer 34 is oriented to transmit an ultrasonic signal 34a radially inwardly toward a concave reflector 38 from which the signal 34a reflects generally forwardly from the tip end of the probe 28, as indicated at 34b in Figs. 4 and 5.

Electrical conductors 40 extend through the probe 28 and connect electrically with the transducers 32 and 34 in order to electrically excite them and to transmit the received information in the form of electrical signals. The pairs of conductors 40 are connected with a pair of electrically conductive strips 42 (see Fig. 3) on the sleeve 24. A pair of slip rings 44 are mounted on the motor shaft 22 and are connected with the respective strips 42 by conductors 46. The slip rings 44 rotate with the motor shaft 22 and are contacted by spring loaded electric contacts 48 which are maintained against the slip rings by compression springs 50 (Fig. 3) .

Electrical signals are transmitted to and received from the contacts 48 by a suitable electrical transmitter/ receiver 52. The electrical contact that is maintained between the contacts 48 and the slip rings 44 allows the transmission of electrical signals to the transducers 32 and 34 and from the transducers back to the transmitter/receiver 52.

Referring again to Figs. 4 and 5 in particular, the reflector 38 is mounted on the end of a support tube 53 that fits slidably in the end 28a of the probe. The support tube 53 has a projecting tongue 54 which fits in a groove 56 formed in the inside surface of probe 28. The fit of the tongue 54 in the groove 56 provides a track system which allows tube 53 to extend and retract axially in the probe 28.

A rigid actuator wire 58 extends through probe 28 and connects with the support tube 53 at one end. As best shown in Figs. 3 and 6, the opposite or outer end of the actuator wire 58 extends into a cylinder 60 forming part of a magnetic actuator 62 which adjusts reflector 38 axially within probe 28. The cylinder 60 extends through an electro magnet 64 forming part of the actuator. Mounted slidably within cylinder 60 and connected with the wire 58 is a magnet 66 which is continuously urged to the right as viewed in Fig. 6 or toward the inner end of the catheter assembly by a compression spring 68.

When the electromagnet 64 is deenergized, the spring 68 maintains the magnet 66 in the position shown in broken lines in Fig. 6. Then, the actuator wire 58 pushes the support tube 53 outwardly to position the reflector 38 as shown in Fig. 5 which is the outer most position of the reflector. However, when the electromagnet 64 is ener¬ gized, the magnetic attraction it exerts on the magnet 66 causes the magnet to retract to the position shown in solid lines in Fig. 6, thus pulling wire 58 and moving the reflector 38 inwardly to the extreme innermost posi¬ tion shown in Fig. 4.

It is thus -evident that the electromagnetic actuator 62 is effective to axially adjust the reflector 38 inwardly and outwardly. As the reflector 38 moves inwardly and outwardly, the ultrasonic signal 34a reflects from dif¬ ferent areas on the curved reflector 38 and thus follows different paths. For example, in the innermost position of the reflector shown in Fig. 4, the reflected signal 34b is reflected across the longitudinal axis of probe 28, while in the outermost position of the reflec¬ tor shown in Fig. 5, the reflected ultrasonic signal 34b is directed away from the longitudinal axis of the probe. The reflected signal 34b forms an acute angle with the longitudinal axis of the probe at all positions of the reflector 38.

With continued reference to Figs. 4 and 5 , the laser beam that is emitted from the tip of the optical fiber 30 is directed toward an inclined mirror 70. The reflector 70 may be oriented to reflect the laser beam onto the curved mirror 38, or it may be oriented to otherwise direct the laser beam out through the tip end of the probe 28.

Figs. 8 and 9 depict an alternative arrangement for axially adjusting the reflector 38. In this arrangement, the mirror 38 is carried on the end of an elongated tube 72 which extends through the probe 28 and rotates with the probe by means of a tongue and groove fit or the like. A bearing 74 is fitted on the outer end of tube 72. The outer race of the bearing 74 has a pair of spaced apart flanges 76 between which a cam 78 closely fits. The cam 78 is mounted eccentrically on the output shaft 80 of an electric motor 82. When the motor 82 is operated, the cam 78 is rotated eccentrically, and its action against the flanges 76 causes the tube 72 to reciprocate inwardly and outwardly by camming action. The bearing 74 allows the tube 72 to rotate when the probe 28 is rotated.

Figs. 10 and 11 depict a mechanism by which the probe 28 may be reciprocated axially relative to the catheter tube 12. An electric motor 84 drives a threaded output shaft 86 which is threaded through the base of a Y-shaped yoke 88. As best shown in Fig. 11, the two arms of the yoke 88 carry rollers 90 which fit closely between a pair of flanges 92 projecting from a spool 94. The spool 94 is secured to a tube 96 that connects with the probe 28.

When the motor is operated in opposite directions, the shaft 68 is rotated in opposite directions to move yoke 88 in opposite directions, thus extending and re¬ tracting the probe 28 relative to the catheter tube 12. When the probe is rotated, the tube 96 and spool 94 are rotated with it, and such rotation is permitted by the fit of the rollers 90 between the flanges 92 of the spool.

In operation of the catheter 10, the catheter tube 12 may be inserted into the artery 14 until the catheter tube end 12a is adjacent to the area of the plaque 16. the probe 28 may be rotated within the catheter tube, and rotation of the probe sweeps the first transducer 32 around so that the signals 32a are swept completely around the circumference of the artery 14. At the same time, the ultrasonic signals 34b which emanate from the other transducer 34 are swept in a circular path in order to provide information as to the character and configura¬ tion of the plaque 16 located ahead of the probe. The reflector 38 can also be extended and retracted in order to direct the signals 34b in different directions to provide an accurate profile of the entirety of the plaque formation. This information is then used to control the laser such that the laser beam emitted from the optical fiber 30 is directed appropriately to destroy the plaque 16 while avoiding damage to the artery walls or other healthy tissue. The probe 28 can be axially ex¬ tended and retracted by operation of the motor 84 if desired.

The ultrasonic transducers 32 and 34 are operated in a pulse-echo mode and are controlled by a computer which controls other functions as well. The information pro¬ vided by transducer 32 determines the thickness of the plaque deposit inwardly from the artery wall and also measures the artery wall thickness to make certain that the laser is not directed toward an undamaged artery wall surface. The two ultrasonic transducers are electrically isolated from one another, and it is possible to use either a single pulse generator to alternately excite the two transducers, or a separate pulse generator for each transducer. The pulse generators may produce spike impulses or square waves of appropriate amplitude and duration to drive each of the transducers at its nominal operating frequency.

A graphic display of the outputs from the transducers may be provided. The display for transducer 34 can include the echo amplitude and time of flight information, and these may be incorporated into a graphic representation of the probe in the artery to show the distance ahead of the probe at which the plaque deposit is detected. The display for transducer 32 will similarly include echo amplitude and time of flight information, and this infor- ation may be incorporated into a graphic representation of the distance from the probe center line to the interi¬ or artery wall as well as the artery wall thickness. The longitudinal and angular positions of the probe may be encoded and used to provide location data that is stored simultaneously with the ultrasonic data. When a probe position is repeated during the course of a particular procedure, the most recent data should overwrite the previous data in order to show how the procedure has changed the condition of the artery. The data may be transferred to memory storage at any time so that before and after comparisons can be later made.

Fig. 12 depicts an alternative arrangement of the compo¬ nents within the tip end of the probe 28. In this ar- rangement, the second transducer 34 is eliminated and the first transducer 32 is arranged in the manner indicated previously. The optical fiber 30 is offset from the longitudinal axis of the probe and is oriented to direct the laser beam toward an inclined mirror 98. The mirror should reflect the laser beam outwardly in a radial direction as indicated by the beam 100 in Fig. 12. A window 102 is provided in the wall of the probe 28 for passage of the laser beam radially through the tip end of the probe.

The catheter depicted in Fig. 12 operates in substantial¬ ly the manner previously described, except that the ultrasonic signals are directed radially at all times, and the laser beam 100 is likewise directed radially for the treatment of plaque or other abnormalities.

Fig. 12a illustrates still another arrangement of compo¬ nents in the tip end of the probe 28. A reflector 103 is mounted in the^' tip end of the probe and includes two sections arranged at a right angle to one another and at 45° to the longitudinal axis of the catheter. The two transducers 32 and 34 emit ultrasound toward the two sections of reflector 103. Transducer 32 emits ultra- sound toward one section of the reflector in a direction to reflect through window 36 in a radial pattern, as indicated at 32a. The other transducer 34 emits ultra¬ sound toward the other section of reflector 103 in a direction to reflect forwardly parallel to the longitudi- nal axis of the catheter, as indicated at 34a.

In the embodiment of Fig. 12a, there are two optical fibers .30 for transmitting laser energy. One fiber 30 is arranged to emit a laser beam which reflects from one section of reflector 103 and through window 102 in a radial direction, as indicated at 100. The other fiber 30 extends through the reflector 103 and directs its laser beam forwardly along the catheter axis.

Figs. 13 and 14 depict another alternative arrangement of the catheter 10. In this embodiment of the invention, the probe 28 is stationary relative to the catheter tube 12. A plurality of the optical fibers 30 extend through the catheter 12 and are arranged around the circumference of the probe 28 in a circular pattern (see Fig. 14) . The tip end of the probe 28 is provided with a conical mirror 104 which is located to receive the laser beams emitted by the fibers 30 and to reflect the beams radially outwardly. Because the fibers are arranged around the entire circumference of the probe, substan¬ tially the entirety of the artery wall circumference can be treated by the fibers. Control of which of the fi¬ bers 30 is to receive laser energy may be effected by a suitable switching system under computer control.

Mounted on the free end of the mirror 104 is an ultrason¬ ic head 106 provided with a phased array of ultrasonic transducers 108 arranged to direct ultrasonic signals radially outwardly around substantially the entire cir- cumference of the probe 28. The electrical conductors 40 extend to the phased array of ultrasonic transducers.

The catheter shown in Figs. 13 and 14 uses the phased array of ultrasonic transducers 108 to provide informa¬ tion as to the configuration and thickness of the plague deposits located radially outwardly from the tip of the probe. The fibers 30 are energized in the desired pat¬ tern with laser energy in order to destroy the plaque deposit while avoiding damage to the artery walls.

Fig. 15 depicts still another alternative arrangement for the tip portion of the probe 28. In this embodiment of the invention, an ultrasonic transducer 110 is carried on the extreme tip of the probe 28 and is oriented relative to the longitudinal axis of the probe at an angle in the range of 4-10 degrees. The transducer 110 emits ultra¬ sonic signals in a conical pattern, with the cone angle determined by the frequency of the electrical signals used to excite the transducer. For example, when the signals are at a relatively high excitation frequency of 20mhz, the cone configuration is indicated by numeral 112 and has a very tight cone angle that approaches the shape of a cylinder. As the frequencies decrease to 5mhz, the cone angle increases as indicated by the conical shape 114. Decreasing the excitation frequency to 3mhz generates the cone pattern 116, and the cone angle is greater yet. In all cases, the major access of the cone makes an acute angle relative to the longitudinal axis of the probe.

A plurality of the optical fibers 30 extend to the tip of the probe and are energized in a selected pattern to treat the occlusion which is sensed by the ultrasonic transducer 110.

Fig. 16 depicts in block diagram form a system which may be used to excite the transducer 110. A variable fre¬ quency oscillator 118 is used in combination with a gated amplifier 120. A pulse width generator 122 controlled by a trigger circuit 124 operates a gate selector 126 which in turn controls the amplifier 120. The output from the amplifier provides a series of radio frequency pulses that are applied to the transducer 110.

The transducer 110 should have a broad band width which is typically 2.5-4 times the nominal center frequency. It may be a single element transducer. Alternatively, a wider frequency range can be covered by using two trans¬ ducer elements, one having a nominal center frequency that is 2-3 times that of the other. The impulse genera¬ tor which excites the transducer is frequency tunable, as previously indicated. It may be a tone burst device that produces a selected number of sinusoidal impulses that have a selected time duration, amplitude and number of impulses. The tone "burst may be produced by the gated amplifier 120 or by a pulsed oscillator. The excitation device may also be a single or multiple square wave generator of selected amplitude, duration and number of square waves in a single burst.

By selectively controlling the impulse characteristics, the transducer is selectively operated at various narrow band frequencies that are within its overall frequency range. For each operating frequency that is used, there is a characteristic beam pattern which defines the volume within the artery from which ultrasonic reflections may be detected, as exemplified by the cone shapes depicted in Fig. 15 as the cones 112, 114 and 116.

The transducer 110 is operated in the pulse echo mode. Returning echoes are characterized by amplitude, time of flight and frequency. This information defines a sector of the artery within which the reflective tissue is located. Lower frequency operation produces a broader ultrasonic beam for impingement on a normal artery wall to produce reflections from relatively thin deposits. Increasing the operating frequency produces a narrower beam that produces reflections only from deposits that protrude farther inwardly from the artery wall . Thus , the highest frequency at which a reflection is received from a particular deposit indicates the thickness of the deposit or the extent of the artery blockage .

A potentially ambiguous response , such as a response from a deposit on the outside curvature at a bend in an ar¬ tery, can be resolved by rotating the probe while sweep- ing through the frequency range of the transducer . The longitudinal and angular positions of the probe are controlled by encoded mechanical devices . The encoders are used to provide location data simultaneously with the ultrasonic data .

The ultrasonic signals should be processed by a receiver/amplifier which may be broad banded in order to cover the entire operating frequency and width. It can incorporate a series of high pass filters that are switched in and out as the transducer excitation frequen¬ cy is switched. Alternatively, a series of narrow to medium band width filters can be used and switched in sequence with a series of discrete excitation frequen¬ cies.

Alternatively, the transducer 110 may be constructed to have a very narrow band width. The transducer can be excited at its nominal natural frequency or at some multiple thereof. This provides a more powerful ultra- sonic output than a broad band transducer, and it may be more suitable for relatively large arteries. However, because a more powerful output produces a longer decay time for the initial pulse, a narrow band width system is relatively insensitive to reflectors that are very close to the probe tip. This problem can be overcome by pro¬ viding the ultrasonic device with separate transmitting and receiving elements which are electrically isolated from one another so that the receiving element does not receive the initial excitation impulse. The receiving element is thus able to respond to reflection that would otherwise be impossible to distinguish from aberrations in the excitation pulse.

It should be noted that with either a broad band width or narrow band width system, an acoustic lens can be added to the face of the transducer to either increase or decrease the amount of beam spread at a given operating frequency and/or to alter the angle of the central ray of the beam with respect to the axis of the artery.

Figs. 17 and 18 depict still another embodiment of the catheter. In this arrangement, the transducer 32 is oriented to direct its ultrasonic signal 32a toward an inclined mirror 128 which reflects the signal in a radial direction through a window 130 in the wall of the probe 28. The reflected signal 32b is directed radially outwardly.

The other transducer 34 is oriented to direct its ultra¬ sonic signal 34a toward another inclined mirror 132. The reflected signal 34b is oriented parallel to the longitu¬ dinal axis of the probe 28.

Transducer 32 thus transmits signals that are oriented radially to determine the thickness of the plaque along the artery wall during rotation of the probe. The other transducer 34 generates a signal forwardly of the probe to provide information as to the plaque deposit ahead of the probe.

The optical fiber 30 may extend through mirror 132 in order to direct the laser beam generally forwardly at a location offset from the longitudinal axis of the probe.

Still another alternative embodiment of the catheter is depicted in Figs. 19-23. Referring first to Fig. 19, a plurality of optical fibers 30 extend from a shutter mechanism 134 and through the probe 28. As shown addi- tionally in Fig. 22, the fibers 30 occupy only approxi¬ mately 1/2 the diameter of the probe 28, with a tube 136 located in the remaining 1/2. The fibers 30 are arranged uniquely such that the fibers whose inner ends 30a are closest to the longitudinal axis of the probe, have their outer ends 30b located farthest from the center of the probe. Conversely, the fibers whose inner ends 30a are located farthest from the center of the probe have their outer ends 30b located closest to the center.

As shown in Figs. 20 and 21, the shutter 134 has a plu¬ rality of pivotal shutter elements 138. When the shutter elements 138 are pivoted fully outwardly, the shutter is fully open, and the ends 30b of all of the fibers 30 are exposed through the shutter. When the elements are pivoted inwardly from the fully opened position, the shutter progressively closes and the shutter opening 140 becomes smaller such that the ends 30b of only some of the fibers are exposed through the shutter opening. The laser energy is transmitted through the shutter opening and is applied to those fibers whose ends 30b are ex¬ posed.

It is noted that as a shutter progressively closes, the fiber ends 30b farthest from the center of the probe are progressively covered by the shutter, and the correspond¬ ing fibers have their inner ends 38 closest to the center of the probe. Consequently, as the shutter closes, the laser energy is progressively transmitted only through those fibers whose inner ends 30a are located closest to the perimeter of the probe 28. As a result, as the shutter is closed, the area within the artery closest to the artery wall is treated last.

The tube 136 is provided with an ultrasonic transducer 142 which is excited through electrical wir¬ ing 144 extending in the tube. The ultrasonic signal 142a emitted by transducer 142 is intercepted by an inclined mirror 146 and reflected by the mirror in a forward direction parallel to the longitudinal axis of the probe, as indicated in Fig. 23 by numeral 142b.

The probe 28 is rotatable in the catheter tube 12, and the tube 136 is rotatable within the probe. consequent¬ ly, by rotating the probe and the tube 136, the ultrason¬ ic signals can sense the profile of the entirety of the artery. Also, the fibers 30 can be directed at the plaque deposits as the probe rotates.

Figs. 24 and 25 depict yet another embodiment of the catheter 10. In this arrangement, a plurality of optical fibers 30 extend through an elongated tube 148 which in turn extends through the probe 28 and is centered on its longitudinal axis. An ultrasonic transducer (not shown) similar to those described previously is carried on the inner end of an elongated tube 150 which extends through the probe parallel to tube 148 but is considerably small¬ er.

The tubes 148 and 150 extend through a stationary cylin¬ der 152. At one end of the cylinder 152, a bar 154 extends diametrically across the cylinder and is fixed to the end of tube 148. A drive roller 156 fixed to tube 150 is mounted for rotation on one end of bar 154 and rolls against the inside surface of cylinder 152. On the opposite end of bar 154, an idler roller 158 is mounted for rotation and rolls against the inside surface of cylinder 152.

The bar 154 can be rotated by any suitable mechanism such as an electric motor (not shown) . As bar.154 is rotated, tube 148 is rotated with it to rotate the optical fibers 30. At the same time, the rolling movement of roller 156 against the inside surface of cylinder 152 causes roller 156 to rotate faster than tube 148 and in an opposite direction, as indicated by the directional arrows in Fig. 25. Consequently, when bar 154 is rotat¬ ed, tube 148 is rotated in one direction and tube 150 is rotated in the opposite direction and at a faster rate. Rotation of tube 150 carries the ultrasonic transducer in the pattern depicted in Fig. 26 so that the transducer is able to direct ultrasonic signals in a manner to sense the configuration of the entirety of the inside of the artery.

Although the various embodiments of the invention have been described in connection with the treatment of arte- rial plaque, it is understood that the catheter can be used in the laser treatment of other medical conditions. For example, tumors and other abnormalities can be treat¬ ed with laser energy in the colon, prostate, esophagus and other organs and internal body parts. It should also be understood that the various ultrasound systems can be used alone as forward looking ultrasound schemes for detecting the configurations in arteries and other inter¬ nal body parts, as well as in combinations with other interactive treatment means such as atherectomy. As one example, the catheter shown in Fig. 23 can be used with an atherectomy device replacing the optical fibers and with the ultrasound system used to help direct the direc¬ tion and control of the atherectomy device.

From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the struc¬ ture.

It will be understood that certain features and subcombi- nations are of utility and may be employed without refer¬ ence to other features and subcombinations. This is contemplated by and is within the scope of the claims.

Since many possible embodiments may be made of the inven¬ tion without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Claims

1. A catheter for insertion into the body to effect medical treatment, comprising: an elongated catheter tube having opposite ends; optical fiber means extending through said catheter tube and terminating adjacent one end thereof for transmitting laser energy to effect said medical treatment; an elongated probe extending through said catheter tube and axially rotatable therein; power means for rotating said probe; ultrasonic transducer means carried on said probe adjacent said one end of the catheter tube for transmitting and receiving ultrasonic signals, said ultrasonic transducer means rotating with said probe and being arranged to direct transmitted ultrasonic signals about the probe during rotation there¬ of; electrical conductor means extending through the probe to the transducer; and means located exteriorly of the catheter tube for applying electrical signals to said conductor means for excitation of said transducer means while said probe is rotating.

2. The catheter of claim 1, wherein said transducer means comprises an ultrasonic transducer oriented to direct transmitted ultrasonic signals in a direction radially of the catheter tube.

3. The catheter of claim 2, wherein said transducer means comprises a second ultrasonic transducer arranged to direct transmitted ultrasonic signals in a direction at an acute angle to the longitudinal axis of the cathe¬ ter tube.

4. The catheter of claim 3, including a reflector in said probe for receiving ultrasonic signals emitted by said second transducer and reflecting the signals in a direction at an acute angle to the longitudinal axis of the catheter tube. 5. The catheter of claim 4, wherein said mirror is curved and including: means for mounting said mirror in the probe for reciprocating axial movement; and power means for effecting reciprocating axial movement of said mirror in the probe to vary the acute angle between the ultrasonic signals and the longitudinal axis of the catheter tube.

6. The catheter of claim 5, wherein said power means for effecting reciprocating axial movement of the mirror comprises: a mirror support carrying said mirror within said probe; an elongated actuator wire extending through the probe to said mirror support for axially reciparocat- ing said support when the wire is extended and retracted; and means for extending and retracting said actuator wire.

7. The catheter of claim 6, wherein said means for extending and retracting said actuator wire comprises: an electromagnet having energized and deenergized condi¬ tions; a magnetic core connected with said actuator wire and disposed within said electromagnet for reciprocating movement between first and second positions at which said wire is respectively extended and retracted; and yield- able means for urging said core toward one of said posi¬ tions, said core moving by magnetic force to the other position thereof when said electromagnet is energized.

8. The catheter of claim 5, wherein said power means for effecting reciprocating axial movement of the mirror comprises: an elongated mirror support tube in said probe arranged for axial reciprocation therein; and power driven cam means located exteriorly of the catheter for axially reciprocating said support tube while accommodat- ing rotation of the support tube when said probe is rotated.

9. The catheter of claim 8, wherein said cam means comprises: power operated drive means having an output shaft; a cam on said output shaft; and a cam follower connected with said support tube in a manner to effect axial reciprocation of the support tube as said follower is axially reciprocated by said cam, said cam follower allowing rotation of the support tube relative thereto.

10. The catheter of claim 1, wherein said power means for rotating said probe comprises: power operated drive means having an output shaft; and means for establishing a connection between said output shaft and said probe in a manner to effect rotation of said probe with said shaft while allowing the probe to be axially extended and retracted relative to said shaft.

11. The catheter of claim 10, wherein said connection is a spline connection.

12. The catheter of claim 10, including power means for effecting axial extension and retraction of the probe relative to said shaft.

13. The catheter of claim l, wherein said means for applying electrical signals to said conductor means comprises: a slip ring on said probe electrically con- nected to said conductor means at all rotative positions of the probe; and means for applying electrical signals to said slip ring from a stationary electrical source while said slip ring is rotating with the probe.

14. The catheter of claim 1, wherein said transducer means comprises: first and second ultrasonic transducers arranged to emit ultrasonic signals directed generally parallel to one another; a first reflector in said probe arranged to receive ultrasonic signals from the first transducer and to reflect the signals in a direction radially of the catheter tube; and a second reflector in said probe arranged to receive ultrasonic signals from the second transducer and to reflect the signals in a direction axialiy of the catheter tube. 15. A catheter for insertion into the body to effect medical treatment, comprising: an elongated catheter tube having opposite ends; a plurality of optical fibers extending through said catheter tube for transmitting laser energy to effect said medical treatment, said fibers being arranged in a circular pattern for selec¬ tively receiving laser energy; a conical mirror adjacent one end of said catheter tube arranged to receive the laser energy emitted by each fiber and to reflect the energy from each fiber generally radially outwardly; ultrasonic transducer means adjacent said one end of the catheter tube for transmitting and receiving ultrasonic signals, said transducer means being arranged to transmit ultrasonic signals generally radially; and electrical conductor means extending through said catheter for excitation of said transducer means.

16. A catheter for insertion into the body to effect medical treatment, comprising: an elongated catheter tube having opposite ends; an elongated probe extending through said catheter tube and axially rotatable therein; power means for rotating said probe; optical fiber means extending through said probe and terminating adjacent one end of the catheter tube for transmitting laser energy to effect said medical treatment; ultrasonic transducer means on said probe adjacent said one end of the catheter tube for transmitting and receiving ultrasonic signals, said transducer means transmitting signals in a conical pattern with the cone angle of each pattern increasing with decreasing frequency of electrical signals which excite the transducer means and with the cone axis of each pattern being oriented at an acute angle to the longitudinal axis of the catheter tube; and means for applying electrical signals to said transducer means at selected frequencies.

17. A catheter for insertion into the body to effect medical treatment, comprising: an elongated catheter tube having inner and outer ends; an elongated probe extending through said catheter tube and axially rotata¬ ble therein, said probe having a circular cross section; means for axially rotating said probe; a plurality of optical fibers extending through said probe for transmit- ting laser energy to effect said medical treatment, each fiber having an inner end adjacent said inner end of the catheter tube and an outer end located exteriorly of the catheter tube; means for arranging said optical fibers in a manner wherein the inner ends of the fibers which are closest to the center of the probe have their outer ends farthest from the center of the probe; shutter means for controlling exposure of the outer ends of the fibers in a manner to progressively expose the outer fiber ends farther from the center of the probe as said shutter means progressively opens, whereby upon closure of said shutter means, the outer fiber ends farther from the center of the probe are progressively blocked from ap¬ plied laser energy; an ultrasonic support means in said probe adjacent the inner end of the catheter tube and axially rotatable therein; ultrasonic transducer means carried on said support means and rotatable therewith for transmitting and receiving ultrasonic signals; and means for rotating said support means.

18. A catheter for insertion into the body to effect medical treatment comprising: an elongated optical fiber tube extending through said catheter tube and coaxial therewith, said optical fiber tube being axially rotata¬ ble relative to said catheter tube; optical fiber means extending through said optical fiber tube and terminating adjacent one end of the catheter tube for transmitting laser energy to effect said medical treatment; an elon¬ gated ultrasound tube extending through said catheter tube and axially offset from the catheter tube axis; ultrasonic transducer means in said ultrasound tube adjacent said one end of the catheter tube for transmit¬ ting and receiving ultrasonic signals; a stationary cylinder adjacent the end of the catheter tube opposite said one end and arranged coaxially with the catheter tube; a bar extending diametrically across said cylinder and fixed to said optical fiber tube, said bar having opposite ends; an idler wheel on one end of said bar in contact with the inside of said cylinder; and a rotatable drive wheel on the opposite end of said bar in contact with the inside of said cylinder and arranged to rotate in a direction opposite the rotation of said bar, said ultrasound tube being fixed to said drive wheel to rotate therewith.

19. In a catheter for insertion into the body, an ultra¬ sound system comprising: an elongated catheter tube having opposite ends; an elongated probe extending through said catheter tube and axially rotatable therein; power means for rotating said probe; ultrasonic transduc¬ er means carried on said probe adjacent said one end of the catheter tube for transmitting and receiving ultra¬ sonic signals, said ultrasonic transducer means rotating with said probe and being arranged to direct transmitted ultrasonic signals about the probe during rotation there¬ of; electrical conductor means extending through the probe to the transducer; and means located exteriorly of the catheter tube for applying electrical signals to said conductor means for excitation of said transducer means while said probe is rotating.

20. The ultrasound system of claim 19, wherein said transducer means comprises an ultrasonic transducer oriented to direct transmitted ultrasonic signals in a direction radially of the catheter tube.

21. The ultrasound system of claim 20, wherein said transducer means comprises a second ultrasonic transducer arranged to direct transmitted ultrasonic signals in a direction at an acute angle to the longitudinal axis of the catheter tube.

22. The ultrasound system of claim 20, wherein said transducer means comprises a second ultrasonic transducer arranged to direct transmitted ultrasonic signals in a direction substantially parallel to the longitudinal axis of the catheter tube.

23. The ultrasound system of claim 22, including a reflector in said probe arranged to reflect the ultrason¬ ic signals transmitted by both said first and second ultrasonic transducers.

24. The ultrasound system of claim 19, wherein said transducer means comprises: first and second ultrasonic transducers arranged to emit ultrasonic signals directed generally parallel to one another; a first reflector in said probe arranged to receive ultrasonic signals from the first transducer and to reflect the signals in a direction radially of the catheter tube; and a second reflector in said probe arranged to receive ultrasonic signals from the second transducer and to reflect the signals in a direction axially of the catheter tube.

25. In a catheter for insertion into the body, an ultra¬ sound system comprising: an elongated catheter tube having opposite ends; an elongated probe extending through said catheter tube and axially rotatable therein; power means for rotating said probe; ultrasonic transduc¬ er means on said probe adjacent said one end of the catheter tube for transmitting and receiving ultrasonic signals, said transducer means transmitting signals in a conical pattern with the cone angle of each pattern increasing with decreasing frequency of electrical sig¬ nals which excite the transducer means and with the cone axis of each pattern being oriented at an acute angle to the longitudinal axis of the catheter tube; and means for applying electrical signals to said transducer means at selected frequencies.