WO2000023125A2

WO2000023125A2 - Catheter for laser treatment of atherosclerotic plaque and other tissue abnormalities

Info

Publication number: WO2000023125A2
Application number: PCT/US1999/024099
Authority: WO
Inventors: Thomas R. Winston; John M. Neet
Original assignee: Intraluminal Therapeutics, Inc.
Priority date: 1998-10-19
Filing date: 1999-10-18
Publication date: 2000-04-27
Also published as: WO2000023125A3; AU6517899A

Abstract

A medical catheter (10) for treating atherosclerotic plaque and other abnormalities includes optical fibers (30) for applying laser energy (100) to the plaque and an ultrasonic transducer system (32, 34) for sensing the location and configuration of the plaque. The optical fibers (30) and electrical wiring 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 direction of the ultrasonic signals. Alternative forms of the invention include different reflector schemes, an angled ultrasonic transducer (110) having a conical signal output that varies with frequency, and various different systems for rotating the transducers and fibers.

Description

CATHETER FOR LASER TREATMENT OF ATHEROSCLEROTIC PLAQUE AND OTHER TISSUE ABNORMALITIES

FIELD OF INVENTION

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 transmission of laser energy and also with an ultrasonic transducer system

for sensing the character and configuration of the area that is to be medically

treated by the laser energy.

BACKGROUND OF THE INVENTION

It has long been known that cardiovascular problems are caused by the

presence of atherosclerotic plaque on the walls of veins and arteries, especially

coronary arteries. For some time, there has been interest in the use of laser

energy to remove plaque and to treat abnormalities on internal organs in the

body. Typically, it is 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 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 transmitting 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 ultrasonic 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 ultrasound 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 arterial 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.

SUMMARY OF THE INVENTION

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

reliability.

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 configuration 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 transducer 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 ultrasonic 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 reflector 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 ultrasonic signals and permits the configuration of the artery

wall around its entire circumference to be sensed without rotation of the

catheter or probe.

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 application 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.

DESCRIPTION OF THE DRAWINGS

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 catheter 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 actuator 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 alternative 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 application 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 invention;

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.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings in more detail and initially 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 ultrasonic 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 outwardly 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 energized, 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 position 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 different

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 reflector 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 86, is

rotated in opposite directions to move yoke 88 in opposite directions, thus

extending and retracting 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 f it 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

configuration 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 extended 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 provided 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 information may be

incorporated into a graphic representation of the distance from the probe center

line to the interior 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 components within the

tip end of the probe 28. In this arrangement, 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 substantially 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 components 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 o 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

ultrasound 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 ultrasound toward the other section of reflector 103 in a direction to

reflect forwardly parallel to the longitudinal 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, substantially the entirety

of the artery wall circumference can be treated by the fibers. Control of which

of the fibers 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 ultrasonic head 106

provided with a phased array of ultrasonic transducers 108 arranged to direct

ultrasonic signals radially outwardly around substantially the entire

circumference 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 information as to the configuration and

thickness of the plaque deposits located radially outwardly from the tip of the

probe. The fibers 30 are energized in the desired pattern 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 ultrasonic 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 axis

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 frequency 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 transducer elements, one having a nominal center frequency that is 2-3

times that of the other. The impulse generator 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 artery, can be resolved by rotating the

probe while sweeping 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 frequency 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 frequencies.

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

ultrasonic 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 providing 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 ultrasonic signal 34a

toward another inclined mirror 132. The reflected signal 34b is oriented

parallel to the longitudinal 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 additionally in

Fig. 22, the fibers 30 occupy only approximately ^lΛ the diameter of the probe

28, with a tube 136 located in the remaining Vi. 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 plurality 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 exposed.

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 corresponding 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 wiring 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. Consequently, by rotating the probe and the tube

136, the ultrasonic 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 smaller.

The tubes 148 and 150 extend through a stationary cylinder 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 rotated, 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 arterial 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 treated 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 internal 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 direction 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 structure.

It will be understood that certain features and subcombinations are of

utility and may be employed without reference 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 invention

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

Having thus described the invention, we claim:

1. In a catheter (10) for insertion into areas of the body such as

arteries, an ultrasonic system comprising:

an elongated catheter tube (12) having opposite ends (12a) (12b) and

defining a longitudinal axis, said catheter tube being flexible to accommodate

insertion into arteries and other areas of the body;

an elongated flexible probe (28) extending through said catheter tube

(12); at least one ultrasonic transducer (32) carried on said probe (28)

adjacent one end thereof for transmitting and receiving ultrasonic signals, and

said transducer (32) being arranged to direct transmitted ultrasonic signals

along a first prescribed path;

a conductive strip (42) extending through said probe (28) to said

ultrasonic transducer (32) for conducting electrical signals thereto;

at least one optical fiber (30) extending through said catheter tube;

a laser coupled to said catheter tube optical fiber (30), said optical fiber

providing a path for transmitting and receiving energy (100) from the laser; and

a reflector (98) carried on said probe , said reflector configured to

reflect energy (100) from said laser along a second prescribed path, wherein

said optical fiber (30) oriented to direct the laser energy toward said reflector.

2. A catheter (10) in accordance with Claim 70 wherein said

reflector (98) reflects the energy from said laser in a direction radial to said

longitudinal axis.

3. A catheter (10) in accordance with Claim 71 wherein said

catheter tube has a window (102) near one end, said reflector (98) positioned to

reflect the laser energy (100) radially outward through said window.

4. A catheter (10) in accordance with Claim 72 comprising:

a first ultrasonic transducer (32) and a second ultrasonic transducer

(34); and

wherein said reflector (103) comprises a first reflector section and a

second reflector section arranged at a right angle to one another and at about 45

degrees to said longitudinal axis, said reflector (103) having an opening

therethrough, said first reflector section arranged to direct the ultrasonic signals

from said first ultrasonic transducer in a direction axial to said longitudinal

axis, said second reflector section arranged to direct the ultrasonic signals from

said second ultrasonic transducer in a direction radial to said longitudinal axis;

and

a first optical fiber (30) and a second optical fiber (30), said first optical

fiber extending through said reflector opening and oriented to direct the energy from said laser in a direction axial to said longitudinal axis, said second optical

fiber (30) oriented to direct the energy from said laser in a direction axial to

said longitudinal axis and toward said reflector (103) first section, said reflector

(103) first section configured to reflect the energy from said laser in a direction

radial to said longitudinal axis.

5. A catheter (10) in accordance with Claim 70 wherein said probe

(28) is axially rotatable within said catheter tube (12).

6. A catheter (10) in accordance with Claim 74 further comprising:

a motor for rotating said probe (28);

at least two slip rings (44) located exteriorly of the catheter; and

at least two contacts (42) movably coupled to said slip rings (44) for

applying said electrical signals to said conductive strip (42) for excitation of

said ultrasonic transducer (32) while said probe is rotating.

7. A catheter (10) in accordance with Claim 74 wherein said

ultrasonic transducer (110) is oriented at an acute angle relative to said

longitudinal axis, said transducer (110) configured to emit the ultrasonic signals

in a conical pattern (112).

8. A catheter (10) in accordance with Claim 76 wherein said

ultrasonic transducer (110) is oriented at an angle of about 4 to about 10

degrees relative to said longitudinal axis.

9. A catheter (10) in accordance with Claim 76 wherein said

ultrasonic transducer (110) is coupled to a circuit (118) (120) (122) (124) (126)

having an output comprising a plurality of radio frequency pulses, said output

characterized by an operating frequency and applied to said transducer (110).

10. A catheter (10) in accordance with Claim 78 wherein said

conical pattern (1 12) has a cone angle determined by said operating frequency.

1 1. A catheter (10) in accordance with Claim 79 wherein said cone

angle (112) decreases as said operating frequency increases.

12. A catheter (10) in accordance with Claim 80 wherein said cone

angle (112) increases as said operating frequency decreases.

13. A catheter (10) in accordance with Claim 78 wherein said circuit

comprises:

a radio frequency gated amplifier (120); a variable frequency oscillator (118) coupled to said gated

amplifier (120);

an impulse generator (122) coupled to said gated amplifier (120)

through a gate selector (126); and

a trigger circuit (124) coupled to said impulse generator (122).

14. A catheter (10) in accordance with Claim 82 wherein said

impulse generator (122) comprises a square wave generator.

15. A catheter (10) in accordance with Claim 82 wherein said

impulse generator (122) comprises a tone burst device.

16. A catheter (10) in accordance with Claim 76 wherein said

ultrasonic transducer (110) has a broad band width.

17. A catheter (10) in accordance with Claim 76 wherein said

ultrasonic transducer (110) has a band width of about 2.5 to about 4 times a

nominal center frequency.

18. A catheter (10) in accordance with Claim 76 wherein said

ultrasonic transducer (110) comprises a single transducer element.

19. A catheter (10) in accordance with Claim 76 wherein said

ultrasonic transducer (110) comprises a first transducer element and a second

transducer element, said second transducer element having a nominal center

frequency of about 2 to about 3 times the nominal center frequency of said first

transducer element.

20. A catheter (10) in accordance with Claim 70 comprising:

a plurality of ultrasonic transducers (108), said plurality of transducers

(108) being arranged in an array to direct transmitted ultrasonic signals radially

outwardly from said longitudinal axis around substantially the entire

circumference of said probe (28);

a plurality of optical fibers (30) arranged in a circular pattern around

substantially the entire circumference of said probe, said plurality of optical

fibers (30) configured to direct the energy (100) from said laser in a direction

axial to said longitudinal axis; and

a conical reflector (104) carried on said probe (28) along said path of

laser energy, to reflect the energy (100) from said laser in a direction radial to

said longitudinal axis.

21. A catheter (10) in accordance with Claim 89 further comprising

a switching system for controlling which of said plurality of optical fibers (30)

receive energy (100) from said laser.

22. In a catheter (10) for insertion into areas of the body such as

arteries, an ultrasonic system comprising:

an elongated catheter tube (12) having opposite ends (12a) (12b) and

defining a longitudinal axis, said catheter tube being flexible to accommodate

insertion into arteries and other areas of the body;

an elongated flexible probe (28) extending through said catheter tube

(12) and axially rotatable therein;

a motor (20) for rotating the probe (28);

at least one ultrasonic transducer (32) carried on said probe (28)

adjacent one end thereof for transmitting and receiving ultrasonic signals, said

transducer being arranged to direct transmitted ultrasonic signals along a

prescribed path;

an axially translatable reflector (38) carried on said probe (28) at a

location along said prescribed path to reflect said ultrasonic signals at an angle

relative to said longitudinal axis; an elongate actuator wire (58) having inner and outer ends, said inner

wire end extending through said probe (28) to said reflector (38) for axially

reciprocating said reflector (38) when said wire (58) is extended and retracted;

an actuator coupled to said actuator wire (58) outer end for adjusting

said reflector (38) linearly in a direction substantially parallel to said

longitudinal axis of said catheter tube (12) to thereby vary, relative to said

longitudinal axis of said catheter tube, said angle relative to said longitudinal

axis at which said signals are reflected by said reflector (38);

a conductive strip (42) extending through said probe (28) to said

ultrasonic transducer (32) for conducting electrical signals thereto;

at least two slip rings (44) located exteriorly of the catheter (10); and

at least two contacts (48) movably coupled to said slip rings (44) for

said ultrasonic transducer (32) while said probe (28) is rotating.

23. In a catheter (10) for insertion into areas of the body such as

arteries, an ultrasonic system comprising:

an elongated catheter tube (12) having opposite ends (12a) (12b) and

defining a longitudinal axis, said catheter tube (12) being flexible to

accommodate insertion into arteries and other areas of the body; an elongated flexible probe (28) extending through said catheter tube

(12); at least one ultrasonic transducer (32) carried on said probe (28)

adjacent one end thereof for transmitting and receiving ultrasonic signals, and

said transducer (32) being arranged to direct transmitted ultrasonic signals

along a first prescribed path;

a first reflector (38) carried on said probe (28) along said first

prescribed path to reflect ultrasonic signals in a direction at an acute angle to

the longitudinal axis of said catheter tube (12);

a conductive strip (42) extending through said probe (28) to said

ultrasonic transducer (32) for conducting electrical signals thereto;

at least one optical fiber (30) extending through said catheter tube (12);

a laser coupled to said catheter tube (12), said optical fiber (30)

providing a path for transmitting and receiving energy from the laser; and

a second reflector (70) carried on said probe, said second reflector

configured to reflect energy (100) from said laser along a second prescribed

path, said optical fiber (30) oriented to direct the laser energy (100) toward said

second reflector (70).

24. A catheter (10) in accordance with Claim 92 wherein said first

reflector (38) comprises a curved mirror.

25. A catheter (10) in accordance with Claim 93 wherein said

catheter tube (12) has a window (36) near one end; and

wherein said ultrasonic transducer (32) comprises a first transducer

element (32) and a second transducer element (34), said first transducer

element (32) configured to emit ultrasonic signals in a direction radial to said

longitudinal axis and outward through said window (36), said second

transducer element (34) configured to emit ultrasonic signals in a direction

radial to said longitudinal axis and towards said first reflector (38); and

wherein said second prescribed path comprises a path toward said first

reflector (38), said first reflector configured to direct said laser energy (100) in

a direction at an acute angle relative to said longitudinal axis.

26. A catheter (10) in accordance with Claim 93 wherein said first

reflector (38) is axially translatable.