US3433226A - Vibratory catheterization apparatus and method of using - Google Patents

Description

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March 18, 1969 c. A. BOYD 3,433,226

VIBRATORY CATHETERIZATION APPARATUS AND METHOD OF USING Filed July 21, 1965 w n y 7 2o 22 et! I a INVENTOI? CHARLES A. BOYD ATTORNEYS.

.-.cludingscoronary atherosclerosis.

United States Patent 3,433,226 VIBRATORY CATHETERIZATION APPARATUS AND METHOD OF USING Charles A. Boyd, West Chester, Pa.,'assignor to Aeroprojects Incorporated, West Chester, Pa., a corporation of Pennsylvania Filed July 21, 1965, Ser. No. 473,596 US. Cl. 128-305 Int. Cl. A61b 17/32; A6111 1/00; A6lm 25/00 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the use of ultrasonic energy for therapeutic purposes, and more particularly to a therapeuticvmethod and apparatus for such purposes as localization and yibratory treatment of irculatioy blocking ..L9 2i 1:@9 z inatieassiiiifi A 4; those occurring in various types of a cl rosis in:

It has been suggested heretofore to use ultrasonic energy in treating patients having subdeltoid bursitis with the energy reportedly being externally applied through the a skin over the affected area via a liquid petrolatum coupling agent, using an intensity of preferably 0.5 watt/ C1132:

ar 1d a maximum of 1.5 watts/cm The ul'fras'onic en e-rgy produces a powerful and deep micromassage, exerts localized thermal action, and increases interacellular me tabolism; it causes exud-ates and precipitates to be absorbed and tissue deposits to be broken up; it loosens tissue, relieves edema, decreases liypertonicity of the muscle, and produces a local analgesia causing an immediate relief of pain. (Page 73, The Indication and Contraindications for Ultrasonic Therapy in Medicine" by J. H. Aldes, in Ultrasound in Biology and Medicine, American Institute of Biological Sciences, Washington. DC, Publication No. 3, 1957) It is to be noted that in this bursitis experimentation, the externally applied ultrasonic energy was ineffective in 52. percent of the cases in decreasing or eliminating calcareous deposit. It has also been suggested (page 161, Ultrasonic Technology by Richard G. Goldman, New York: Reinhold Publishing Corp., 1962): r

It is interesting also to speculate on the possibility of inserting a small transducer into the stomach or heart, which can then irradiate gall stones or calcinations at close range with localized effect.

Moreover, at page l6l of the July-September 1964 3,433,226 Patented Mar. 18 1969 issue (vol. 2) of Ultrasonics, in a Letter to the Editor, there was reported an unsuccessful attempt to apply ultrasonic energy with the end object of emulsifying atherom atous material while leaving the strong fibrous coat of the artery intact or re-boring atheromaobstructed arteries too small for conventional endarterectomy. Thus, postmortem specimens of arteries affected by various degrees. of atheroma were irradiated in water with ultrasound for at least 30 minute periods at frequencies of 20 kc. and l mc. using 50 and 60 watts of power with piezoelectric crystals, and also at 13 kc. using up to 100 watts of power with an industrial magnetostrictive transducer. There was no obvious effect whatever in the 13 kc. experiments, and the only macroscopic effect in the 20 kc. and 1 mc. experiments was co'agulation partly due to "heat.

In other work, a commercial general-purpose apparatus (advertised to enable production of a widerange of effects in chemistry, biology, pharmacology, metallurgy, etc.) was impractical for blood vessel decalcification. Touching a solid acoustical coupling member probe (part of an. ultrasonic apparatus having a design frequency of 20 kc.' and a maximum average output of watts) to atheromatous placques for 15-20 seconds resulted in decimation of the placques; however, there was shearing of the silver braze joint joining the probe to the remainder of the apparatus. Further experiments, with a catenoidal coupling .mem-ber attached to the same basic apparatus, with an in--*- p'u't'to the transducer of 9 watts (power level), readily cleared atheromatous material from cadaver coronary vessels but, after one minute of ultrasonic energy application, tissue heating with destruction of specimens was often apparent.

The present invention overcomes the disadvantages of the prior art and indicates that tissue heating can be eliminated by using a hollow internally cooled catheter. Excellent results on atheromatous aorta tissue were 'obtained by passing ambient saline or a low molecular weight dextran solution through the probe. 0n cadaver coronary vessels, the atheromata was reduced to micron size particles using a power level of 2.6 watts. Said par ticles can then be flushed away by use of a dextran solution.

It is an object of .the present invention to provide novel apparatus and method for vibratory catheterization.

It is another object of the present invention to provide an ultrasonic catheter for internal therapeutic purposes.

It is a further object of the present invention to provide a catheter for decimation of atheromatous placques without hetiting tissues or destruction of specimens.

Another object of the present invention is to provide apparatus for Treatment of coronary artery disease by u sonic coronary endarterectomy.

For the purpose of illustrating the invention there is shown in the drawings a form which is presently preferred, it being understood, however, that this invention is not limited to the precise arrangements and instrumentalitie's shown.

FIGURE 1 is a sectional view of a catheter.

FIGURE 2 is a sectional view of the tip end of another embodiment.

FIGURE 3 is a sectional view of the tip end of another embodiment.

Referring to the drawings, wherein like reference characters refer to like parts, there is shown'in FIGURE 1 an ultrasonic catheter generally designated as 10.

The catheterlg is essentially an ultrasonic transducercoupling system comprising an ult rasonic transducer 12, an acoustical coupling member 14, another acoustical coupling member 16, and a third acoustical coupling member 18 having an end face or tip 20. Member 18 is hollow and metallurgically joined to merriber 14 in line with passageway 22. Passageway 23 intersects passageway 22. Conduit 24 is connected to member 14 in passageway 23.

Catheter is designed to operate at a given frequency, which is preferably a resonant frequency. Catheter 10 is preferably dimensioned to have an over-all physical length equivalent to an acoustical length of a whole number multiple of one-half wavelength in the material of which it is made at the said frequency (see FIGURE 1 wherein "n" indicates a whole number). For efficient operation, there is an antinode (loop) area of the vibration at the end face 20.

Transducer 12 may be of the magnetostrictive type as shown and of conventional construction comprising a half-wavelength long laminated core of nickel, nickel-iron alloy, or other magnetostrietive material, properly dimensioned to insure axial resonance with the frequency of alternatlng current applied thereto by coil 1 -1 so as to cause it to increase or decrease in length according to its coefiicient of magnetostriction. The detailed construction of a suitable magnetostrietive transducer is well known to those skilled in the art and does not form a part of the present invention and, accordingly, no description of its construction will be made herein. It will be appreciated by those skilled in the art that in place of the magnetostrictive transducer 12 other known types of transducers may be substituted; for example, an electrostrictive or piezoelectric transducer made of bariuriftitar'iate, quartz crystals, lead zirconate titanate, etc., may be utilized.

Transducer 12 is provided with an excitation coil '11 and a polarizing coil 13. Excitation coil 11 is connected to a power supply (incorporating an amplifier, not shown, and oscillator, not shown) suitable for powering the transducer 12; such equipment is well known to the art. The desirability of magnetically polarizing the magnetostrictive transducer 12 by means of polarizing coil 13, in order for the metal laminations in said transducer to efiiciently convert the applied energy from excitation coil 11 into elastic vibratory energy, is also readily understood by those skilled in the art. Low voltage direct current can be supplied to coil 13 by battery, rectifier, or other means well known to the art.

The aforesaid power supply system, in a typical example, is capable of producing electrical signals in the range of between about 60 cycles per second and about 300,000 cycles per second. This frequency range is suitable for purposes of the present invention, including as it does frequencies in both the audible range (such as up to about 15,000 cycles per second) and the ultrasonic range (generally above about 15,000 cycles per second). A preferred frequency would be in the range of from about 3,000 to about 50,000 cycles per second with the optimum being between about 14,000 to about 35,000 cycles per second. Normally, a frequency is chosen which will provide a suitable size of apparatus for a given application or set of applications, with the ultrasonic range having the further advantage of inaudibility for operator comfort.

Thus, catheter transducer-coupling system 10 may be constructed to operate at 28,000 cycles per second, for example. In an embodiment of FIGURE 1, a 100 watt power supply was used to drive a transducer 12 at said 28 kc. design frequency.

As is well known to the art, the electrical frequency of the alternating current power supply (sirch as 60 cycles per second) is changed to match the mechanical or elastic vibratory frequency of the transducer (28,000 cycles per second in this example, as aforesaid).

The member 18 is preferably semi-flexible and can be curved within certain limits established by the acoustic characteristics to facilitate manipulation. Preferably, the curvature of the member 18 has a bend ra'dius which is at least x/4 wherein X is the wavelength of the material of member 18. The reason for this limitation on the bend radius is set forth rnore clearly in Patent 3,166,840.

'A coolant fluid may be introduced through conduit 24 and passageway 2]. to cop] the member 18, to irrigate tis sue in the vicinity of the tip 20, and flush away any micron sized particles resulting from decimation of placques. A low molecular weight dextran solution at a temperature of from about ambient temperature to body temperature may be pumped through the system at low pressure. The solution exits through the tip 20. The micron sized particles of the placques result from the physical effect of the vibrating catheter tip 20 upon calcified atheromata.

Sterilization of the catheter can be accomplished utilizing conventional sterilization equipment. If desired, the member 18 may be provided with removable tips which can be disposable. In order to facilitate sterilization or autoclaving, and simultaneously facilitate manipulation of the catheter with minimum power losses, a force-insensitive mount 15 is provided. One end of mount 15 is metallurgically joined to the coupling member 14. The other end of mount 15 is free. The mount 15 is provided with a radially outwardly directed flange 17. Flange 17 is joined to a housing 25 with a waterproof joint. Housing 25 may constitute a handle and is preferably of sufiicient length so as to encase the transducer 12 as shown. Suitable plug-in connections 27, 27' can be provided hermetically sealed to the housing 25 for electrically connecting to the coils 11 and 13, and to facilitate autoclaving the catheter.

A force-insensitive mount may comprise a sleeve such as the described in US. Patents 2,891,178; 2,891,179; and

2,891,180. The disclosures of such patents are incorporated herein by reference. Such a mount facilitates the application of force necessary to insert the catheter into a cavity, artery, or the like. The sleeve is made from a metal such as steel or any other suitable resonant material and has a length equal to a single one-half wavelength. The sleeve surrounds 'the coupler 14 and is concentric therewith and spaced therefrom.

The flange 17 is spaced from the free end of mount 15 by an acoustical distance corresponding to one-quarter wavelength according to the properties of the mount and the desired frequency of operation. The mount 15 when so constructed .will cause a true node of vibratory energy to be developed in the flange 17 so that no vibratory energy will be transmitted to the housing 25.

The operable usage of the ultrasonic endarterectomy catheter requires that a reliable source of vibratory energy be coupled to the working tip 20 having a diameter of the order of a millimeter. The members 16 and 18 may have a length of around 18 inches. To prevent temperature build-up and thereby minimize thermal damage to the tissue, a cooling system as described above is required.

The vibrational energy generated by the transducer can be coupled to the members 16 and 18 in several different modes. The first and simplest mode is that of longitudinal vibration, as shown, wherein the particle displacements occur in a direction parallel to the axis of members 16 and 18. A second mode of vibration is that of lateral or transverse vibration wherein particle displacements occur in a direction normal to the axis of members 16 and 18. This results in an excursion of the tip 20 parallel to the plane of the end face thereof. Other more complicated modes including torsional vibration wherein the system oscillates periodically in torsion about its own axis, or a radial vibration wherein the end tip 20 periodically ex= pands and contracts radially may be utilized.

The exact mechanism by which the placques of the calcified atheromata are destroyed is not well understood. The nature of the mechanism will depend in part on the physical characteristics of the vibrating tip. Several tip geometries may be employed where desired: In FIGURE 1, the geometry of the removable tip 20 is a square edge. As shown more clearly in FIGURE 2, the tip 20 remov= ably mounted on a coupling member 18' may have a chisel edge defined by an internal beveled surface 26. In FIGURE 2, the beveled surface 26 provides a sharp cut ting edge at the periphery.

A third type of tip is illustrated in FIGURE 3. Tip 20' removably mounted on coupling member 18" is in 53 bulbous form, The bulb 28 may be either metal or plastic. The purpose of bulb 28 is to provide a more positive contact between the working surface of the catheter and the tissue being treated. The surface of bulb 28 may have an abrasive character. The tips of FIGURES 2 and 3 may be substituted for the tip 20' in FIGURE 1.

The method steps and conditions for practicing the present invention for treatment of disease or other conditions for therapeutic purposes is considered to be suf ficiently known to those skilled in the art so as not to require a detailed explanation. Using the known principle of oxygen in solution, at 3 atmospheres positive pressure ischemia induced by introducing the catheter by way of the coronary ostia can be prevented. The flow of coolant, such as low molecular weight dextran, can replace oxygenated blood for long periods and prevent a means of oxygenation to the myocardium.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims rather than to the foregoing specification as indicating the scope of the invention,

It is claimed:

1. A catheter comprising a transducer means for gen erating vibratory energy, a resonant coupling member having one end connected to said transducer and a tip at its other end. the end of said tip being at an anti-node on said member, said member having an acoustical length of a whole number multiple of one-half wavelength in the material of which it is made at the frequency of said transducer means, and said member being partially hol= low with the hollow portion beginning at said tip, whereby a liquid for cooling said member may be pumped through said portion for discharge through said tip.

2. A catheter in accordance with claim 1 including a housing, said member being hermetically sealed to said housing with said transducer means disposed within said housing.

3. A catheter in accordance with claim 1 wherein said 6 transducer means is axially coupled to said member for vibrating said member in a direction corresponding to the longitudinal axis of said member.

4. A catheter in accordance with claim 1 wherein said tip has an end face which is substantially perpendicular to the longitudinal axis of said member. F

5. A catheter in accordance with claim 1 wherein said tip is bulbous.

6. A catheter in accordance with claim 1 wherein said tip has an internal beveled face providing a sharp-edge at the periphery of the tip.

7. A catheter in accordance with claim 1 wherein said coupling member has a length of approximately 18 inches and a diameter along a substantial length thereof beginning at the tip of approximately 1 millimeter.

8. A method comprising the steps of transmitting acoustical vibratory energy from a transducer means through a resonant coupling member at least a portion of which is hollow beginning from a tip end of said coupling member designed to have an anti-node at the end face of the tip, introducing a coolant through said portion for dis-' charge through said tip, and transmitting the vibratory energy from the tip to a living animal by contacting the portion of the animal with said tip.

References Cited UNITED STATES PATENTS 2,230,997 2/1941 Chambers et al. 2,407,690 9/1946 Southworth. 3,358,677 12/1967 Sheldon 128-24 FOREIGN PATENTS 540,428 4/1922 France. 991,494 6/ 1951 France.

L. W. TRAPP, Primary Examiner.

US. Cl. X.R. HS-24, 348

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