CA2128006C - Ultrasonic transmission apparatus - Google Patents

Abstract

(see fig. 1) A horn (12) connectable to an energy source (88) to amplify ultrasound displacement is connected to a transmitter (14) formed of material having relatively high mechanical Q for transmitting ultrasonic energy therethrough at a frequency f, the transmitter having a horn-shaped configuration of length that is a multiple of a half-wavelength .lambda./2, and preferably this horn-shaped configuration is comprised of multiple horn segments (16a and 16b) each of a length substantially equal to a multiple of .lambda./2, where .lambda. = c/f (c is the speed of sound in the high Q material). The transmitter has a proximal end of cross-sectional diameter D1 connected to the horn and a distal end of cross-sectional diameter D2, where D1 > D2. Ultrasonic energy transmitted through the transmitter drives a tip which is coupled to the transmitter by means of a flexible connector (20).

Description

2 12 ,?~
W~93/1~6 ~ CT/US93/00764 ULTRASONIC TRANSMISSION APPARATUS
BACKGROUND OF THE INVENTION
This invention relates to ultrasonic transmission apparatus and, more parti ularly, to such apparatus which 5 transmits ultrasonic energy from a source to a distal tip with minimal loss, and which is particularly adaptable for medical applications.
The field of balloon angioplasty provides ~n established techni~ue for reducing vascular obstructions caused by thrombi and plague deposits. ~ere, a catheter having an inflatable balloon at its distal end is inserted into a patient's blood vessel and then, by us~ of a guide wire, in cooperation with an observation system, the catheter is advanaed until it reaches the obstruction (e.g.
a thrombus) in question. Then, the balloon is inflated with the hope of reducing the obstruction. Unfortunately, balloon angioplasty, although offering a desirabl~
alternatiYe to arterial bypass surgery, suffers significant drawbacks. For example, khe procedure is neither eff~ative :: 20 nor safe in cases of thrombus. Thrombus often is not destroyed by the infIated balloon, thus resulting in ~: relatively q~ick re-occlusion. In addition, balloon ~; angioplasty often is accompanied by significant damage to ~he blood vessel which further stimulates thrombus formation 2~ and:re-occlusi~n.
: Other catheter-based procedures have been proposed as alternatives to bypass surgery, such as laser-type angiopla~ty, mechanical drills and~ most recently, ultrasonic angîoplasty. :One example of ultrasonic angioplasty apparatu is describ d in copending application serial numb~r 44g,465, assigned to the same assignee as the presenk ihvention.
In a typical ultrasonic angioplasty device, a long, thin ultrasonic trAn.~itter connects a tip at its di~tal ~nd to a pow~r sourcs at it~ proximal end. U~ing s~n~rd angiopla~ty t~ ni ques, ~his transmitter is ins~rted into and guided through the patient's blood ves ~l until the distal ip arrives at the occlusion. Then, sner~iza~ion of ~he power source produces ~ltrasonic WO93/16~6 2 1 2 ~ O ~ ~ -2- PCT~U~93/0~764 displacement that is transmitted to the tip, resulting in destruction of the thrombus. However, and as found in the ultrasonic angioplasty apparatus described in U.SO Patent 4,870~953, the transmission of ultrasonic anergy through the ultrasonic tran~mitter could generate an inordinate amount of he~t which, if not remcved, could result in serious damage to the patient's blood vessels. Accordingly, the apparatus described in U.S. Patent 4,870,953 provides a cooling arra~gement in which the ultrasonic transmitter is dispo-c~ in a cooling bath, namely a cathe~er that is flushed with a physiologic solution to cool the entire transmitter.
It has been found that heat generation is common to most material heretofore used for ultrasonic angioplasty because those materials produce significant attenuation of the ultrasonic energy. Consequently, acoustic energy is transfonmed to thermal energy. For the purpose of coronary prccedures, the ultra~onic energy must be transmitted over a ; distance on the order of a~out 12~-150 cm.; and the 2~0~ attenuation presented by this length of material requires an ex~remely high input energy level in order for sufficient ult~asonic displacPment to be produced at the tip, : The~efore, the hea~ generated by the typi al ultrasonic : angioplasty device increases the probability of material 25: fatigue which may result in fracture of the device while in use.
;: The aforementioned patent application 449~465 is ;directed to a novel arrangement which overaomes th2se drawbacks, ~ van~ages and hazards. As disclo~ed th~rein, 0~ :th~ ultrasonlc tra~smitter is fQrmed of material h~ving a high ~ec.h~ical Q, ~hus minimizing the attenuati~n xperienced by the ultrasonic energy as it is transmitted ..
:tl.~ou~ll this transmitter and thereby minimizing he~t generation. Pr~ferably, altlmi nllm or an aluminum alloy~ ~ ; :35 having a me~h~~~cal Q greater than 50,Q00 is u~ed. Exampl of sui able alloys include duralumin, hiduminium, AL-7075, AL-2024 and AL-6061. The generation of heat is subs~antially obviated; and it no longer is necessa~y to use W0~3/16~6 _3_ 2 ~ 2~ PCT/~IS93/0~7~

an ultrasonic source of high en~rgy levels in order to drive the transmitter.
While the aforementioned ultrasonic angioplasty devi~e obtains benefits and results not pre~iously realized, further investigation into ultrasonic angioplasty has l~d to certain observations, culminating in the in~ention disclosed herein.
It has been found that the cross-sectional area of the ultrasonic transmitter directly affects the attenuation of the ultrasonic energy transmitted thereby. That is, a greater cross sectional diamet~r results in less attenuatian of the transmitted ultrasonic energy, thereby permitting the use of an ultrasonic energy source having a lower energy level. But, an ultrasonic transmit~er of greater cross-sectional diameter results in a more rigid transmissionmember which may not be able to follow easiiy the bends inherent in typical blood vessels.
It also has been found that an ultrasonic ~: ~ t~n~itter of reduced cross sectional diameter formed of high~me~h~nical Q ma~erial may be susceptible to easy f~acture or fatigue. Thus, although a very thin ultra~onic :transmitter may ~Yhihit suf~icient flexibility, it also presents an extremely high risk of breakage due to fatigue : and to significant bending thereof as it follows a blood :~ 25 ; ve~sel.
: : It has been observed, that, when a physician uses a ~ypical ultrasonic angioplasty device, he manually guides it:into the patient~s blood v~ssel and, more often than not~
gr~sp~ a portion of the transmission member while ultrasonic 3 0 en~rgy is transmitted therethrough . This presents a problem b~cau e it re~ult~ in substantial dampirlg of ultrasonic displacement, thereby seriously reducing the operating ef f iciency of t~e device .
Although many conventional ultras :>nic: medical 35 instruments, such as an ultrasonic scalpel, operate at ~requencies in the range 2 0-3 0 kHz, it has been f oulld that such f requellc:ies do not permit maximum displacement at the tip of the apparatus when the device is bent. However, the h~ gher frequencies neaded ~or more optimum displacemenl:

W093/l6~6 ~1 2 ~ 4 PC~/US~3/0~764 present more difficult desi~n parameters, they result in greater attenuation of the transmitted ultrasonic energy and, for the same displacement, they produce greater internal strass which increases the tPndency of the transmitter to fracture due to fatigue. On the other hand, however, a higher ultrasonic frequency permits the transmitter to be subjected to a sharper bend without as significant an energy loss as at lower frequencies and, thus, the use of such higher frequencies in an ultrasonic I0 angioplasty device permits that device to be used in blood vessels and lumens having tighter turns.
It also has been observed, that since patient ~:
safety is of the highest priority, care must be taken in the deei~n of the ultrasonic angioplasty device to ~;n;rize hazards and risk of injury to the patient in the event of a malfunction or break in the device. :
OBJECTS O~ THE INVENTION
Therefore, it is an object of the pr~sent invention to p~ovide improved ultrasonic transmission apparatus which minimizes the attenuation of ultrasonic energy tr~n~r;tted therethrough, thus permitting the use of an ultrasonic source of reduced energy level. :~
Another object of this invention is to provide ultrasonic transmission apparatus which f inds particular application in coronary procedures as well as in other : ~rocedures in which the apparatus follows ~urved or tortuous paths.
~- A further object of this invention is to provide an ultrasonic transmitter for generating optimal ultrasonic dispIacs~ent a$ its distal tip while being connected at its proximal end to an ultrasonic source of r~duced energy ' 'l~vel.
Still another object of this invention is to provide an ultrasQnic angioplasty device having desirable flexibility, maximum tip displacem~nt and minimal ~nergy loss as ultrasonic energy is transmitted from a suitable source to the tip, An additional objezt o~ t~is invention is to provide an ultrasonic angioplasty device formed of material ~ 0 WO93/16~6 -5- PCT/VS93/007 having a high mechanical Q and P~hihiting good resistance to fatigue and ~racture.
It is a furth~r object of ~his invention ~o provide an ultrasonic angioplasty device which ge~erates minimal heat and is provided with a safety feature to prevent injury to the pa ient in the event that the angioplasty device breaks.
Another object of this invention is to pro~ide an ultr2sonic angioplasty device having a.distal tip configured to ~imi ze cavitation in the fluid in which the davice i used~
- Various other objects, advantages and features of the present invention will become readily apparent from the ensuing detailed description, and the novel features will be particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
In a~cordance with this invention, improved ~: ultra~onic trans=ission apparatus is provided with a horn ~: conn~ctable to an energy source for amplifying ultrasound di~placement and a ~r~n~itter formed of material having relatively high m~ohAnical Q for transmitting ultra onic ene~gy th~rethrough at a frequency ~. The transmitter e~hihits a horn-shap~ configuration of length that is : substantially a multiple of a half-wavelength of A/2, and preferably the transmitter is comprised of multiple horn segments, each having a length substantially e~ual to a multiple of AJ2, where A equals c/f and c is the speed of sound in the material. The transmitter has a proximal end crogs-sectional diam~ter Dl connected to the horn and a ~: ~ 30 distal end o~ c:ross-sectional diameter D2 where I)~ > D2. A
: tip driven by the ultrasonic energy i~ coupled to the ~ Itran~mitter ~y way of a flexible connector which transmits ..
ultr~sonic enexgy th re~hrouyA. In a pre~erred embodim~nt, the flexibl~ connector is comprised of plur~l wires~ each o~
a diameter l~ss than D~, and ~ach wire h~ving a first end.
conn cted to the distal end of the tr~n~;tter and a s~cond end conneGted ~o the tip for tran~ferring t~ the tip ultrasonic energy recei~ed from the tr~n~ tter.

212 ~ ~ O ~ -6- PCl/US93/0~764 The wires of the f lexible connector may be coupled directly to the distal end of the transmitter; but in one embodiment, a base member is provided for effecting this connection~ In this embo~; m~"t, the base member comprises a generally cylindrical housing having at one end a central recess of a diameter substantially equal to D~ to receive the distal end of the transmitter, and at the other end plural recesses each of a diameter substantially equa~l to that of each wire for receiving the first ends of the plural wires.
As an aspect of this invention, the plural wires are isolated ~'rom each other, as by being disposed in respective tubular channels which may be formed of individual tubes or, alternatively, the tubular channels may be comprised of a multi-lumen conduit. Preferably, the tubular channels are open at their opposite ends and are formed of flexible material such that they and the wires : ~ disposed therewithin are adapted to follow the bends of a .~
patient's bloo~ vessel. The open ended tubular channels 20 ~permit the i~ ction thereinto of a suitable fluid, such a~s saline solution. This solution reduces the ultrasonic a~ on the transmitter; and additionally prevents backflow of, for e~rle, the pati~nt's blood.
As a ~eature of this invention, a sleeve is ; ~25~ ~disposed a~out at least those segments Qf the transmitter e~r~ted to be inserted into the blood vessel. It is c ed ~hat in~:use,:the transmitter will be inserted into '~
a~:guid~ catheter that i8 inserted into ths patient's blood vessel. The distal end of the sleeve is secured to the ;tubular c~nnels~surrounding the wires, there~y providing a it ~or the aforementioned fluid.
As an aspect of this featurP~ fluid is ~upplied to ~ : thQ slee~e by an input conduit coupled thereto~ and a valve :~ : in ~luid comm~nication with the proxir~l end portion of the : 35 51~V~ acts to ~e~ent backflow of fluid through the slaeve.
In a pre~erred embodiment, the input conduit includes a c~upIing ç~n~el ~or coupling the proYir-L end p~rtion of the sleeve to the horn, and the valv~ comprises a manually tightened cap coaxial with the horn and disposed ~ver the ~ 1 2 ~
W~93/16~6 -7- PCT/US93/007 coupling channel and the horn and located a~ a node of longitudinal ultrasonic vibration.
As another a pect of this invention, a proteotive cover or sheath is disposed over at least one segment at the proximal end of ~he transmitter, and terminates substantially at a node of ultrasonic vibration in the transmitter. Henoe, a user, such as a physician, is enabled to grasp the proximal end when guiding the transmitter into a lumen with~ut contacting the transmitter directly. This avoid~ substantial damping of ultrasonic vibrations of the tr~n~;tter. Preferably, the se~ment (or segments) over which the sheath is disposed, is pro~ided with an~ular :shoulders located ~t u}trasonic vibration nodes to contact the sheath in the event the sheath is deformed.- When the : 15 apparatus is disposed in a guide catheter which is inserted into ~he patient's blood vessel, the doctor advances the tran mitter so that the distal end of the apparatus, namely ~: the tip, extends beyond the guide catheter into contact with r or proximate, a thrombus or other obstruction to be ~:~; 20~ ~removed~ The:length of the protective sheath preferably is : a:fun~tion of the location of the nodes of ultrasonic vibration. Since~,~ in a preferr~d ~rho~iment, this sheath is r~latiYe}y rigid, its length influences ~he overall ,~
f~lexibility of the~transmitter and it should be as short as : 25 lS practical because its rigidity tends to reduce the flexibility of;the~transmitter. However~ its length should b~:equal to the distance the physician is expei~ed to move ~; :the~tip bey~nd: the end of thP guide catheter.
Preferably, fluid is supplied ~rom a suitable ;3~0~ source to the protecti~e shea~h whiah is in :Eluid communication with the sl~e~e and which, in turn, is in f luid c~ catio~ with the tubular channels surroundîng the wires o~ the ~lexible connector.
In a p~eferred embodiment, the transmitter is 35: formed of aluminum and the wires of the flexible connector are formed of titanium.
As anoth~r feature of this invention, the tip : eYh;~its incr~c~A sur~ace area so as to increase cavitation. In one ~ho~iment~ the tip is comprised of WO93/16~6 2 1 ~ ~ O O 1~ -8- PCT/US93/00764 proximal and distal ~ylindrical por~ions which are in~erconnected by an intermediate portion having a thickness less than the diameter of each of the proximal and distal portions, ~hus increasing the surface area of the tip.
Differen~ tip shapes and configurations are disclosed. For example, the distal portion of the tip may be of substantially truncated semi-spheroid shape, and the proximal portion may be of cylindrical shape. The distal portion may include a concave face. In another example, the distal portion of the tip may be mushroom-shaped. In yet another e~le, the distal portion of the tip may exhibit a "double mushroom" shape.
BRIEF DESCRIPTION OF THE DRAWINGS
The following detailed description, given by way of example and not intended to limit the present invention solely thereto, will best be understood in conjunction with the accompanying drawings in which: -FIG. l is a side view of ultrasonic transmission : apparatus in accordance with the present invention;
2~ FIG. lA illustrates the tr~n.~r;tter of the present invention;
FIG~ ~B is a graphical representation of the r2lationship between displa ement and length of the : transmitter of FIG. lA;
~: 25 FIG. ~ is a sectional view of the sleeve, :~ protective sheath and fluid coupling channel in the vicinity of the proximal end of the ultrasonic transmission apparatus shown in ~IG. l;
FIGS. 3A ~D are vie~s ~f respective portions of :~ 30 the flexible connector and tip of the ultrasonic transmission apparatus;
i FIG. 4 is a schematic illustration of an ultrasonic system ready for use by a physician;
FIGS~ 5A 5C are respective views of the base member that m~y be used with the ultrasonic transmission apparatus of the present invention;
FIGS. 6A and ÇB illustrate one embo~im~nt of the t~p that may be used with the present invention and FIG. 6C
illustrates an alternative thereto; and .. .. . . . .

WO93/16646 9 ~ 8 i~ ~ G PCT/VS93/007 FIGS. 7A-7K illustrate various alternative embodiments of the tip that may be used with the present invention. :~
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, wherein the like reference numerals are used throughout, and in particular to FI~. l, there is illustrated a preferred embodiment of ultrasonic transmission apparatus in ~ccordance with the present invention. For convenience, this apparatus is shown ~-and described herein in the environm~nt of an ultrasonic angioplasty device readily adapted to be guided into a lumen of a patient~ referred to generally herein as the patient's blood vessel, fo~ the purpose of destroying a thrombus therein. ~t will be appreciated, however, that the ultrasonic tr~n~ission apparatus disclosed hPrein admits of different applications and need not be limited solely to ~--coronary thrombosis angioplasty or evPn to medical : applications.
~ As shown in FIG. l, ultrasonic tr~n~m;ssion :~ 20 apparatus l0 is comprised of a horn 12, a transmitter l4, a tip~18 and a flexible connector 20 for connecting tip 18 to transmitter 14. FI~. l also illustrates surrounding tubing in:~which the ultrasonic tr~n~ission apparatus is disposed. :~
: The purpose and const ~ ~tion of this tubing is described : 25 hereinbelow. :-~ , A desirable objective of ultrasonic transmission :-apparatus l0 is:to generate reciprocating movement of tip l8 along:the longit~ n~l axis of the ultrasonic transmis~ion ~'~
~: apparatus, referred to as longi~ in~l displacement of the ti~. :Th~ apparatus ha5 been designed to provi~e maximum di~placement of tip 13 while re~uiring minimal input energy ; to achie~e that displacement. For example, desirable tip : ~ displacement is~on the order of abQut 20~ to 60~ p~ak~to-peak, at ultra~anic ~requencies, and in one application, this displacement is about 30~, The overall length of the appa~atus fr~m the proximal end of horn 12 to tip 18 disposed at the distal end of the ultrasonic transmission apparatus generally is in the range o~ l00 ko 150~m., and : for most patients, this length is about 140cm for W~93/16~6 2 1 2 8 3 0 ~ -lo- PCT/~IS93/007~

intracoronary procedures. In other applications, this length may be shorter or greater.
It is appreciated that ultrasonic energy which is supplied to horn 12 from a suitable energy source will undergo substantial attenuation over the length of the ultrasonic transmission apparatus. Therefore, to achieve the desirable tip displacement without requiring very high (and potentially harmful) input energy transmi~tPr l~ has ~een d~signed to minimize such attenuation. This is a hieved by constructing transmitter 14 of a material having a ~ery high m~ nical Q, such as on the order of ~0,000 or greater. One ~ le of a suitable material is aluminum or an aluminum alloy, such as AL-7075, AL-2024, AL-6061, duralumin and hidumini~m, as disclosed in ~opending application serial number 449,465. In addition, in the preferred embodiment, transmitter ~4 is formed of multiple horn se~ments distributed along the length thereof. The :: horn segments may be exponential, s~epped, or ~Yh ihit other profiles vr shapes known to those of ordinary skill in the : 20 art. Preferably, each segment has a length substantially ~equal to a multiple of Aj2, where A=c/f, f is the frequency :of:the ultrasonic energy supplied to the trAn-~;tter and c the speed of sound in the material. The horn segments :need not eYh~hit equal lengths, and a thicker segment pro~ides less attenuation than a thinner segment. Alsol in 'the:preferred ~hoA;rent, segments that are substantially :strai~h~, that is, where the diameter at the proximal end therec~f is equa~ to the diameter al: the distal end, ar~
interspers~d with: the horn se~ments. H re too, the length ~: 30 of each straight segment is eqlaal to a multiple o~ A/2; and it is een in FIG. lA that horn segments 16a alternate with ~traight se~r~nts 16b. Such alternation of horn and ..
traight segm~nts results in what ~s re~erred to herein as a ~r~gular distribution of horn segments along the length of tran mitter 14. The length of a horn segment ~6a need not be equal to the length of an adjacent straight segment 16~;
and it will be appreciated that segments 16b need not ~rily be straight.

W~93/16~ h~ PCT/~'S93/0~764 The lengths o~ the horn and straight segments 16a and 16b at the proximal end of the transmitter may be longer than at the distal end because the larger diameter of these segments at the proximal end provides less displacem~nt loss. Also, since the longer, thicker segments are less flexible, it is preferable in coronary applications for the dist~l end of the transmitter to be more flexible and thus follow the turns of the pati~nt's blood vessel.
It has been found that each horn segment 16a acts a~c a transformer analogous to an electrical transformer and functio~s to increase the displacement produced in response to a gi~en level of input ultrasonic energy. A ~raphical representation of the manner in which the displacement along khe length ~f trAn.critter 14 varies in response to a given input ultrasonic energy level is shown in FIG. 1~. Whereas each horn segment 16a tends to increase the displacement that may be produced in responsP to this inpu~ energy level, each interspersed, or straight segment 16b simply attenuates that displacement. The displacement at the distal end of , ::20 the transmitter may be reduced relative to the displac~ment that may be produced at its proximal end, but it will be seen that this reduc~ion, or attenuation, is far 1BSS than would otherwise be achieved if tr~n.cr; tter 14 was of , constant, uniform cross-sectional dimension, as represented --by~ t~ attenuation~characteristic in FI~. lB~
x Since ultra~onic transmission apparatus 10 is i~tended to be usad in a patient's blood ve~sel, its dasign ~.
subject to inherent constrain~. For example, the : :: thickness or cross-s~ctional diameter, of tr~n~itter 14 ~must be sufficient to be placed within the patient's blood -~ ~ vessel, and in part~cular, the tran~mitte~ must be thin ~nough to be disposed within a guide catheter.
As anot~er example~ transmitter 14 cannot be so ~hiak as to be too rigid and thus not capable of f ollowing 35 the normal turns and hen~l~ of a 1: lood vessel ,. Although a v~ry thiIl transmitter would satisfy the need ~or a ~lexible devic:e that passes easily within t~e patient' s blood vessel, a thin transmitter of constant cross-sectional diameter results in unacceptable attenuation of the ultra~onic ~093/l6~46 ~ 1 2 ~ O ~ 6 -12- PCT~US93/~0764 displacement, thus requiring a much higher level of input ultrasonic ener~y to produce a desired displacement. In addition, even when m~terial with a high mechanical Q i~
used, the amount of input energy which is needed for a thin transmitter of constant cross-sectional diameter to achieve the desired tip displacement generates heat which is harmful and presents a serious risk of injury to the patient.
Furthermore, a material such as aluminum, although ~Yh; hiting a desirably high mechanical Q is relatively brittle; and the tensile stres~ exerted by its ultrasonic displace~ent in combination with the need for a thin tr~ritter to follow the turns and bPnds of a blood vessel may result in fracture of the transmitter.
The foregoing difficulties are minimized by providing alternate segments 16a and 16b, as illustrated, thus ~;nirizing attenuation of the ultrasonic displacement, and permitting the cross-sectional diameter of transmitter 1~ to be reduced from a relatively large diam ter Dl at its proximal end to a relatively small diameter D2 at its distal : 20 endO ~hus, khat portion of transmitter 14 which must be flexible in order to follow the turns and bends of a patient~s bl~od vessel, namely the dis~al p~rtion, ~y~;hits reduced diameter to enhance flexibility; and the use of horn segments (even at the distal end thereof) provides improved 25 : attenuation characteristics, as shown in FIG. lB. In one embodiment, diameter ~ at the proximal end of the fixst : horn segment 16a is on the order of about 1.6mm and diam~ter D2:a~ the dictal end of transmitter 14 is on the order of : a~out 0.63mm. Although a transmitter f~rmed of a single horn-shaped configuration whose overall length is a multiple ~f A/2 may be u~ed, such as a singl~, continuou~lyltapered member of 100-150 cm in length, this single horn s~gment doe not provide attenuation characteri~tics as fa~orablé as ths pr~ferred emhodi~nent formed of horn and ~traight ~
35 ~;egments distributed substantially regularly along the l~ngth o~ ~he transmitter.
Although each horn and straight segment has a length equal to a multiple of A/2, this multiple ~m) need not be the same f or each segment . ~hus, the length of a WO 93Jlfi~6 -13- 2 l 2 8 '~ fi PCT/US93/00?~

segment may be recognized, generally, as mi 1/2 where i=l, 2, 3, etc.
However, since the length of each segment is a multiple of A/2, it is seen that adjacent segments join at displacement antinodes. It will be appreciated that these junctions are relatively smooth an~ do not present discontinuities from one segment to the next. In one embodiment, tr~nsmitter 14 is of integral one-piece construction; and may be machined from a single block of material or, alternatively, may be extruded.
Returning to FIG. 1, horn 12 is coupled to the proximal end of transmitter 14 and, in the prefer~ed embo~iment, the horn and tr~ncm;tter are of integral one-piece construction. Alterna- tively, howa~er, the transmitter may be otherwise secured to the horn, as by a suitable adhesive, welding, screw or other mechanical means normally used to csnnect components in an ultrasonic device.
: :Horn 12 is proYided with a hand piece connector 24 at its proximaI end for receiving and coupling th~reto a hand 2:0 piece, such a hand piece 86 shown in F~G. 4. This hand piece includes a conventional transducer to convert ele;~trical energy to ultra~onic acoustic ~nergy and thereby drive horn 12.
: As also shown in FIG. 1, horn 12 is provided with~: 25 a pair o~ annular shoulders 26 disposed at an ultrasonic displacement node (tha~ is, the di placement nod~ is located between shoulders 26), these shoulders being adapted to ~: ~rece:ive an o-r~ng, such as 0-ring 44 shown in FIG. 2, for :providing a fluid-ti~ht seal in a fluid supply channel 28, as will be described. By providing shoulders 26 at a node, th~ presence of this seal does not signi~icantly affect the , . ~ I , displacement of transmit~er 14.
: The distal end of the tr~n~;tter i coupled to tip 18 by flexible connector 20. From the preceding 35 ~ Fion~ it is appreciated that the dis~al end of ultrasonic transmission apparatus 10 is expected to be ; ~ubject to greater h~n~ing angles than the remainder of the apparatus as it i~ inserted into ~nd through a blood vessel.
: Consequently, ~lexible connector 20 should exhibit high w~ g3/16~6 2 ~ 2 ~ 14- ~T/~'S93/~0~

flexibility, yet it should be strong enough to withstand internal stress created by the ~ransmission of ultrasonic energy therethrough. These requirements are met by constructing flexible connector 20 as a plurality of thin wires secured to the distal end of transmitter 14. In the pr~ferred embodiment, the flexible connector is formed of a plurality of titanium wires; and any suitable number of wires will suffice. Preferably, 3 or 4 parallel wires are used, and as described hereinbelow in conjunction with FIGD
3, an embodiment utilizing four wires is shown. The diameter of each wire is less than the cross-sectional diameter D2 of the distal segment included in transmitter 14. In one practical embo~i~p~t the diameters of the titanium wires are uniform, and the diameter D3 of each titanium wire is on the order of abou~ O.27mm.
Optimally, each of these titanium wires is secured directly to the end face of the distal segment included in transmitter 14, or, alternatively, is integrally formed with ~;
the distal segment of the transmitter. Moreover, it would ~be best if each wire is configured as a horn to act as a ~: transformer for the ultrasonic displacement transferred thereto. However,;such direct connection of a titanium wire t~ or integral fabrication of such a wire with the distal ;~ end of transm~tter 14 presents substantial mechanical and assembly difficulti~s; as does ~he forming of a thin .
tit~nium wire with a horn configuration. Accordingly, in ~: the emh~i~cnt illustrated herein, a base member 22 is used to connect the titanium wires to the transmitter. The base m~mher may b~ fo~med of the same material as transmitt~r 14 and as will be described in greater detail in FIG. 5, : includes a central recess 92 (see FIG. 5A) to receive the distal segment of transmitter 14, and also includes a : plurality of recesses 94a, 94b,.... to receive respective ones of the conne tor wires.
In addition, to facili~ate assembly of the ultra~onic transmission apparatus, central recess 92 of ba~e me~her 22 ~ ; hits uni~orm diamet~r D2 to receive dis~al segmen~t 16b, which is a straight segment. The length o~ ~
this distal segment and, thus, the length of recess 92, is WO~3/16~6 -15- ~ i 2 8 0 ~- g PCT/US931~07fi4 less than A/2. Accordingly, it will be appreciated from FIG. 1 that the last segment 16a upstr~am of base member 22 is a horn segment to act as an ultrasonic displa~-e~nt transformer. Distal segment 16b (as best seen in FIG. lA) which is inserted into recess 92 of base member 22, is of minimal length sufficient to provide a mechanically secure connection of the base member to tr~nC~;tter l~. Since this distal segment 16b and the titanium wires attenuate t~e ultrasonic displacement, it is desirable to m;nir;ze the total length of this distal segment and the titanium wires.
Nevertheless, if the length of flexible connector 20 is represented as L, the length of base member 22 is represented as Lb and the length of tip 18 is represented as : Lt (as shown in FIG. l), then L + Ib + Lt = k A'/2, where k is an integer and A' is the eff ective wavelength in the section formed of the base mem~er (described herein as aluminum), the flexible connector ~described as titanium) and the tip (described as aluminum). In the example described her~in, this :effective wavelength is determined p~imarily by the wavelength in aluminum and the wavelength in titanium~
In use, it is expected that the wires comprising fle~ible connector 20 wil~ bend to follow the configuration :~ ~ Q~ the blood vessel in which the appara~us is used.
25 ~Consequently, con~act between adjacent wires is likely.
Such~contact produces unwanted damping of ultrasonic displacç-~nt and the:generation of excessive heat~
~ ; Accordingl~, to preYent such contact, the titanium wires are : ; i ol~ted from each okher, and in one embodiment, this is achieved by disposing the wires in respective tubular ~h~nnels which may be formsd of, for e~Am~le, individual flexible tubes or, alternatively, a multi ~h~nnel (or multi-lumen) conduit~ Such tubes or tllh~ r hannels may be formed of plastic, rubber or other ~on~entional ~lexîble mat~rial nor~ally used in medical applications. As will be : d~scribed below/ such tubes or tubular channels provide not only me~h~nical isolation of the wire~ but ~lso enable fluid to flow therethrough for the purpose of reduciny the ultrasonic load on the transmitter, 2S well as preventing WO9~/16~6 Q, , 16 PCT/US93~00764 ~ ~ 2 ~
backflow of blood through the conduit in which the transmitter is disposed. This fluid, such as saline, reduces transverse vibration of the connector wires and provides lubrication for longitudinal displacement of the wires. Further description of flexible connector 20 is described in conjunction with Figs. 3A-3D.
It is desirabl~ to provide a plurality of wires in connector 20, even though, theoretically, only one wire will suffice, because a single wire may not be capable of transmitting sufficient ultrasonic energy at desirably thin diameters and because of the improved safety factor P~h;~ited by plural wires. Since the material from which the wires are formed preferably exhibits a tensile strength coefficient higher than that of the material from which tran~mitter 14 i5 formed, the risk of fatigue due to ultrasonic movement and bending of the connector is relatively low. Nevertheless, by using plural wires, the likelihood that all of the wires will fracture : simultaneously is minimal. Thus, since flexible conn~ctor : 2~ 20 couples tip 18 t~ transmitter 14, the use of plural wires substantially minimizes the risk that the tip will break :~ awa~ from ~he tr~n~itter.
: ~ ~ In addition, it has been fsund that plural wires are capable of transmitting more ultrasonic energy th~rethrough. Hence, the input energy supplied to the :~ apparatus may be reduced without decreasing the operating efficiency o~ the transmission apparatus.
Tip 18 is reciprocally driven at ultrasonic ~re~uencie~ for the desirabls objective of creating ~avitation in the patient's blood vessel. When adjacent a thrombus, such cavitation tends to dislodge dead red blood cell~ which are trapped in the fiber matrix of the thrombus, thu~ dîsper~ing the thrombus and eliminating the blockage.
Furthermore, by reason of this cavitation, and particularly because of the shape o~ tip 18, the rele~s~ red blood ce~ls are x~u~led harml~ssly to the patient's blood stream and the ~ibers are destroyed. In other applications, however, cavitation may not be of significant importance and the tip will be suitably ~haped.
. .

.'3 ~ ~ G
WO93~16~ -17- PCr/VS93/00764 To optimize desirable cavitation, tip 18 is configured to have increased surface area. A preferred embodiment of the tip is illustrated in FIGS. 6A, 6B and 6C, and other embodiments are shown in FIGS. 7A-7K. As will be described, the preferred embodiment of tip 18 includes a proximal portion connect~d to the wires included in flexible connector 20, a distal portion having, preferably, a concave face, and an intermediate portion which connects the proximal and distal portions and which eYh;hits a thickness less than the diameter of either the proximal portion or. the : distal portion. In this embodiment, in addition to h~ving a concave face, the distal portion of tip 18 is of a substantially truncated semi-spheroid shape, whereas the proximal portion is generally cylindrical. By providing the intermediate connecting portion between the proximal and distal portions with reduced thickness, a discontinuity in the 5urface of the tip is created, and this discontinuity : increases the surface ar~a in a direction perpendicular to : ~ the direction of displa~ement, as best shown in FIG. 6A.
: ~ ~ 20 As ~een in FIG. 1, transmitter 14 is disposed in sleeve :40 which provides a channel for fluid to flow about the transmitter. Sleeve 40 is formed of flexible material, ~: : such as rubber, pl~stic or other suitable material commonly used in catheter~ for medical applications. The distal end ~:25 ~f sleeve 40 is coupled to the tubular channels that urro~nd the wire~ of~flexible connector 20. This coupling may be achieved by an adhesive, by thermal bonding, or by o~her conventional means for providing a fluid tight conn~ction of the sleeve to the tu~ular channels. Sleeve 40~~ 30 also pr~vides contai~ment for transmitter 14 in the unlikely event ~hat the transmitter fractures. Hence, the leeve : reduces risk of in~ury to the patient and facilitates rapid or emergency removal of the ultrasonic tr~ ission apparatus ~rom the patient's blood vessel.
: 35 The proximal end of sleeve 40 is coupled to ~;
protective sheath 38 with a fluid ight bond. The protective sheath provides a continuation of the fluid : channel which surrounds transmitter 14. In a preferred embodiment, protective sheath 38 should be fo~med of WO9~/16646 -18- P~T/US93/~0764 ?., 1 ?~
material which is sufficiently strong as not to deform when grasped by a physician. It will be appreciated that when the illustrated ultrasonic tr~n.~mission apparatus is advanced in a patient's blood vessel, there is a tendency for the physician or technician to grasp the proximal end of transmitter 14 for guiding the transmitter surely and stably. It is likely that the physician would contact a portion of the transmitter at a location other than a vibration node; and such contact would substantially damp the ultrasonic vibrations of th~ transmitter. Howe~er, by pro~iding protective sheath 38, the grasping thereof by the physician will avoid contact betwe~n the physician's fing~rs and a ~e~m~nt ~6a, 16b, and such avoidance of direct contact will prevent damping of the ultrasonic vibrations. Hence, protective sheath 38 performs a dual function, namely, it is included in the fluid conduit which surrounds transmitt~r 14, and it also provides protection against the damping of : ~ ultrasonic ~ibrations due to contact of the transmitter by the physician~ It will be seen tAat th~ lenyth of 2~ protective shea~h 3B should be such that it ends at an ultrasonic vibration node. Also, its length preferab~y should~be short because its rigidity reduces the flexibility o~ the tr~n.s~;tter, but nevertheless shou~d be sufficient to permit the physician:to advance the transmitter by an amount which moves tip 18 out of a guiding catheter with which the : : tr~n~itter may be used and into proximity with a thrombus.~ ~ : Spacers:37 may be provided on tr~n~ritter 14 at displacem~nt node to prevent sheath 38 fr3m csntacting the transmltter ~ven if th~:sheath is deformed by the physician. These ~5pacers may be 5houlders formed on th~ transmitter, as shown in FI~. 2 . It will be appreciated that, in normal use, the transmitter i~ inserted into and mo~ed through a guide aatheter of standard length. The guide catheter is provided 3S with one or more hemo~tasis valv~s, located at positions 5uch that these valves contact protectlve sheath 38 just as tip 18 emerges from the distal end of the guide catheter.
At this location, ~he tip is spaced from the thrombus or obstruction. It is expected that the physician will advance W093/16~6 19 P~T/US93/00764 the transmission apparatus to bring tip 18 adjacent to or in contact with the obstruction, and then he will energize th~
ultras~nic transmission apparatus. Thus, the transmitter is moved further into the guide catheter and the length of sheath 38 should be at least equal to this distance over which the tr~n.c~itter is moYed.
Since the cross-sectional diameter of tran5mitter 14 gradually decrea~es from its proximal end to its distal end, the interior volume of the fluid channel which surrounds th~ transmitter increases. Although it is desirable to reduce the diameter of the protective sheath and the sleeve gradually as well, this may result in an expensive custom design which would increase ~he cost of the apparatus. Conse~uently, protective sheath 38 exh?; hits uniform inner and outer diameters and, likewise, sleeve 40 ~hihit~ uniform inner and outer diameters. Of course, the innex diameters of the sleeve and the protective sheath are greater than the maximum cro~s-sectional diameters of th~se s~gments 16a and 16b inc?uded therein so as to provide the fluid conduit surrounding these segments.
The proximal end of protective sheath 38 is in fluid communi~ation with a suitable fluid source supplied ~: the~eto by a Y-shaped coupling channel 30. As illustrated in FI~. 1, and ~s~will be described in connectîon with FIG. -:
25~ ~ 2~ ~coupling ~hAnnel 30 is disposed about at least the distal por~ion o~ horn 12 and is coupled to protecti~e sheath 38 ~y an input conduit 36. A syringe c~nnector 32 ~unctions to connect :~a syringe or other suitable source of fluid to s::ouplin~ chann~l 30~ Thus, fluid may flow fr~m the fluid SOU~;8 to syringe ~cormector 32, tc~ coupling channel 30 and thrsugh input conduit 3 6 to protective sheath 3 8 . Horn 12 exhibits an exponentially tapered prof ile and coupling c:hannel 3 0 i8 secured in a ~luid-ti~ht manner to the horn .
Sus:h ~luid-tight connection is provided by a cap ~4 which cooperates wi~b coupling ~hAnnel 30 and O~ring 44 to ~chieve a ~luid-tight ~eal. It will be appreciatad tpat coupling c~nrl~l 30 may be a conventional hemostatic adapter.
Bef ore describing the mann r in which ~he ultrasonic transmission apparatus is used and operates, WO93/1~6 ~ 2 ~ -3 &, -20- PCT/~S93/00764 reference is made to FIG. 2 which illustrates, in gre~ter detail, the fluid conduit that surrounds transmitter 14 for supplying fluid from a suitable source to the tr~nc~itter.
A portion of sleeve 40 is illustrated, and the proximal end of the sleeve is secur~d to the distal end of protective sheath 38. In the illustrated embodiment, the outer diameter of the proximal portion of sleeve 40 is adhesively secured to the inner diameter of the distal portion of the protective sheath. Althou~h not clearly shown, it will be recognized that the protec~ive sheath extends over one or more segments of transmitter 14 and preferably ends at a displacement node. The proximal end portion of protective sheath 38 is adhesively ~ecured to input conduit 36 located at the di~tal end of Y-shaped coupling channel 30. As~ 15 mentioned above, and as clearly shown in FIG. 2, coupling ahAnnel 30 includes a fluid supply ~hAnnel 32 which, as previously referenced and as shown more particularly in FIG.

4, i~ connect d to a syringe 84 by means of a luer lock : ~onnector 48. Thus, fluid from the syringe or, alternatively, any other desired fluid source, is supplied to ~leeve 40 by way of lu~r lock connector 48, fluid supply ch~n~el 32, coupling channal 30, input conduit 36 and :;
~ pro~ecti~e sheath 38.
: FIG. 2 clearly illustrates O-ring 44 disposed at~ ~ 25 the location defined:by annular shoulders 26 on horn 12.
oupl:ing ch~n~el 30 includes a stepped inner diameter which f~rms~a ledge disposed~against O-ring 44. The O-ring i5 sand. iched between this ledge and an annular spacer 46 that is~:positioned about horn 12 and is disposed within coupling ~ 30 ch~n~el 30. ~he proximal end of the coupling channel is :: pro~ded wit~ screw threads that ma~e with cap 34, the ~ ~ " , I .
latter ha~ing a neck which extends within the coupling :~ ~h~nn~l into con~act with spacer 46. It is seen that :~ coupling ~h~nnel 30, input conduit 36, O-ring 44, spacex 46 and cap ~4 all are co~Yi~l with the longit~ n~l axis of : horn 12.
To ef~ect a fluid-tight seal such that fluid in the chA~l de*ined by protective sheath 3~ and input :: conduit 36 does not leak from cap 34, it will be seen that, WOg3/16~6 -21- J~ J '5~' PCT/US93/007 as the cap is tightened on the proximal end of coupling channel 30, the neck of the cap drives spacer 46 against 0-ring 44. Hence, a fluid-tight seal is formed between the 0-ring and the ledge formed interiorly of coupling channel 30 to prevent fluid from passing beyond the 0-ring and leaking from cap 34.
Turning now to FIGS. 3A-3D, the con~truction of flexible connector 20 and the manner in which the fl~xible connector joins tip 18 to transmitter 14 are shown in greater detail, It will be recognized that FIG~ 3A is a magnified side view of fl~xible connector 20, FIG. 3B is a sectional view of tip 18 taken along sectiQn lines B-B of FIG. 3A, FIG. 3C is a sectional view of the flexible : connector taken along section lines C-C o~ FIG. 3A and FIG.
3D is a sectional view of FIG. 3A. In the illustrated embo~;ment, the flexible connector is comprised of four wires 50a, 50b, 50c and 50d, although any other desired number of wires may be used, such as three, five, etc. The wires 50a 50d are symmetricall~ arranged, and each wire is -~
20 surrounded by a flexibla tub~ 54a, 54b, 54c and 54d, esp~ctively. Although individual, discrete fl~xible tubes ar~ illustrated in ~IGS. 3A, 3C and 3D, a single multi-lumen onduit may be used as an alternative, ~s ment~oned above.
: For~oonvenience, however, the tubular channels which 25:~surround wires 50a-50d will be described as individual, exible tubes.
ires 50a 50d ~yhihit high tsnsi~ e strength to minimize ~he l~kelihood of fracture due to ~atigue or stress. ~s mentioned above, a d~sirable material from which 30 the wires may be formed is titanium. Thus, tha wires may be !~ su~iciently thin so as to follow eaRily the bends of a blood ve ~el, but~because of the high tensil~ 5trength thereo~, ~uch wires are quite strong. ~eYertheless, and as de8cribed above, to minimize the risk of tip 18 breaking :~ 35 aw~y ~rom tr~nsmitter 14, a plurality o~ such wires is used.
: As al~o discuc~ above, the use of plural wires increases t~e leYel o~ ultrasonic energy that can be tranemitted~ thus ~reducing the input energy level that need be supplied to the tr~~cm~tter for a desir~d tip displacement. It will be seen WO93/16646 2 ~ 2 8 o ~ ~ -22- PCT/~93/0 in FIG. 3D, and will be described further below in connection with FIG. 5, that the proximal ends of wires 50a-50d are secured to base member 22 and the distal ends of these wires are secured to tip 18.
In addition t~ the plural connection wires 50a-50d and their respective flexible tubes 54a-54d, a central guide wire conduit 56 is included in flexible connector 20. Those of ordinary skill in the art will recognize that, when the ultrasonic transmission apparatus is inserted into the patient's vessel ~umen, a guide wire first is inserted through the vessel lumen, and the ultrasonic transmission apparatus is threaded onto this guide wire so as to be guided therealong through the lumen. To accommodate this guide wire, tip l~ is provided with a central conduit, and lS guide wixe conduit 56 extends into this central conduit and through flexible connector 20. FIG. 3D best illustr~tes the : ~ positioning of this g~ide wire conduit, and FIG. 3C shows that guide wire conduit 56 is symmetrical with wires 50a 50d and their respectlve flexible tubes 54a-54d. Preferably, 20~ the~proximal end:of~guide wire conduit 56 terminates near :the~proximal ends~of flexible tubes 54a-54d, as seen in FI~,.
3D:,~ to facilitate the emergence of guide wire 58 from the ~:~ : flexible connec~or~ ~As best seen in FIG. 4, it is preferred hat the guide wire be external to sleeve 40 and ~rotective ~:
25~ sheath 3~.
m As shown in F~G. 3D, the length of flexible tube-e 54a-54d is less than the length of the respective wires 50a-50d disposed ther-within. Consequently, dist~l openings ~:
64a-64d of these flexible tubes are spaced from tip 18 and 30~:t~e fluid, such~as saline, supplied thereto from coupling c~n~el 30 (as aforedescribed in connection with FIG. 2) prevents fluid from flowing from the patientf s blood ves~el into the ~lexible tubes. FIG. 3D also illustra~es the : proximal ends of each of flexible tubes 54a-54d being ~he~iVely ~cured in fluid-tight relation to ~leeve 40~ In one embodiment, the sleeve surrounds all of the ~lexibl~ .
~ub~s; and FIG. 3D illustrates that the proximal ends of the ~lexible tub~s may b~ provided with a shoulder for rec~iving and s~curing the distal end of the sleeve.

. .

W093/16~6 -23- ~ '-~l~b~}~ ~ PCT/VS93/00764 Tip 18 is illustrated as having a distal portion 66 of a truncated semi-spheroid shape. The tip also includes a proximal portion, which is illustrated as being substanti~l~y cylindrical, with an intermediate portion 70 connecting distal portion 66 to proximal portion 68. FXGS.
3A, 3B and 3D show that the thicknes~ of intermediate portion 70 is less than the diameters of distal portion 66 and proximal portion 68. As a result, the surface area of tip 18 is increased, particularly in the direction normal to the direction of displacement, by reason of the discontinuity therein presented by interme~iate portion 70 This discontinuity creates a cavitation surface 72 on proximal portion 68 and an opposite, facing cavitation urface 78 on di~tal portion 66. Oth~r examples of tip configurations having cavitation surfaces are illustrated in FIGS~ 6C and 7A-7K.
As best seen in FIG. 3D, proximal portion 68 is provided with recesses 76a, 76b, 76c and 76d adapted to receive and secure the distal ends of wires 50a, 50b, 50c and 50d. It is reco~nized, therefore, that the diameter oP
: : recesses 76a-76d is substantially equal to the outer ~:~ diameter of wires 50a-50d, respectively. The wires may be adhesively secured within recesses 76a-76d; and it will be appreciated that other conventional means may be used to a~fix the wires to proximal portion 68.
FIG. 3D also illustrates the proxi~al ends of wires 50a-50d being secured within rorresponding rec~ses of base member 22, with the base member including a central recess in which di tal segment 16b o~ transmitter 14 i5 ~: 30 ~ecured. Thu~, and as described above~ ba~e member 22 functions to connect transmitter ~4 to flexible connector ~0 .
It will be seen that, as di~tal se~ment 16b of transmitter 14 undergoes reciprocal displacement at ultrasonic freguenaiss, wires ~Oa-50d lik~wis are displaced reciproc~lly, ~hereby driving tip 18 at ultrasonic frequencies. Cavitation is produced ~y the ultrasonic displacement o~ the tip to destroy a thrombus in the patient's blood vess l.

W~93/1~6 2 ~ ~80Q~ -24- PCT/US93/007~

Turning to FI~. 4, there is illustrated an embodiment o~ an ultrasonic system incorp~rating the ultrasonic transmission apparatus of the present invention which is seen to be connected to an ultrasonic anergy source 88 and to a fluid supply ~yringe 84. Here, a handpiece 86 is s~cured to handpiece connector 24 of horn 12 (FIG. l) and an electrical connector extends from ultrasonic energy source 88 to the handpiece. The handpiece includes an acoustic transducer and is energized by energy source ~8 to supply ultrasonic energy to the horn of the tr~n.C~itter, thereb~ driving tip 18. FIG. 4 also illustrates guide wire 58 on which tip 18 and flexible connector 20 are threaded, the guide wire serving to guide the advancement of the ultrasonic transmission apparatus through the patient's blood vessel to the vicinity of a thrombus that is to be removed. Normally, ultrasonic energy source 8~ is deactivated when the illustrated ultra onic transmission apparatus is threaded onto guide wire 58 and advanced t~erealong through the patient's blood vessel. Hence, 20 ~during this advancement of the apparatus, the physician may .
grasp any portion of transmitter 14 without any adverse affect.
When tip l~ is disposed in the vicinity of the thrombu~ to be removed, as will be observed by conventional ~5 fluoroscopic techniques known to those of ordinary skill in the art, ultrasonic energy source 88 is activated. In the pre~erred embodiment, ultrasonic energy is transmitted at a frequency in the range of 40 kHz to 60 kH~, and in the applicatisn described herein, this fr~uency may be about 45 : 30 KH~, resulting in~reciprocal displacement of tip 18 on the order of 20~ to 60~ peak-to-peak, and in the describsd applic~tion, about 30 ~. At this time, the physician should not grasp any o~ sagments 16a, 16b directly~ It is : appreciatsd that uch direct contact of:the physician's fil~el~ with t~fie segments will produce substan~ial damping of the ultrasonic displace~ent. But, by reason of pro~ective ~heath 38, the physician may hold transmi~ter 14 to pro~ide steady and stable guiding thereof as he adv~nce~
tip l8 toward the thrombus while the tip is being W~93/16646 -25- 2 2 (~ ~ ~ 6 PCT/US93~0~7 ultrasonically displaced. It is expected that, by grasping protective sheath 38, the physician will advance transmitter 14 unti~ tip ~8 i5 proximate the thrombus; and as mentioned above, he length of the sheath is sufficient to accommodate this advance. Continu~d ultrasonic vibration of the tlp produces cavitation that destroys the thrombus, an~ the danger of releasing the thrombus, or a significant portion thereof, to travel through the patient's circulatory system i~ minimized. It should be recognized that tip design influences the flow pattern of fluid adjacent the thrombus, such as the patient's blood, saline supplied from syringe ~4 ~as an eY~rle of a suitable source) or a mixture thereof.
In the present application, tip 18 is configured to enhance cavitation and to draw the thrombus toward the tip.
However, in other applications o~ this invention, cavitation may be merely incidental and the tip is designed accordingly.
By reason of flexibIe connector 20, the distal : ~ portion of the ultrasonic trAns~ission apparatus is readily capable of following the bends of the patient'~ blood vessel~ The use of thin, flexible wires of high t~nsile ; : strength minimizes the risk of fracture, m;~ es the risk that~tip 18 will break away from transmitter ~4 and improves the ultrasonic energy transmission chara~teristics of the connector. Moreover, by forming transmitter 14 of high-Q
material, the attenuation of ultrasonic displacement is ~ mini~ized and, advan~ageously, minimal heat is generated.
- : The use of multiple horns distributed along transmitter 14 - ampli~ies ultrasonic displac~?nt. Consequ~ntly, ultra~onic ~ne~gy source 88 may exhibit a lower ener~y level to attain ; jthe ~ame displacement of tip 18 than would otherwi5e be the case i~ significant attenuation occurred in tr~n~m;tter 1~.
Although not shown herein, it has been di~cussed above and, thu~ , it will be apprecia~ed that in most applications a guidi~g catheter i~ used with guide wire 58, and the illustrated ultrasonic transmission apparatus is d~sposed within that guiding cathater. O~ course, the physician pushes the apparatus so that tip 18 emerges from he guiding catheter and the length of protective sheath 38 W093/16~6 2 ~ 23D~36 -26- PC~/US93/007~

sh~uld be sufficient to accommodate this movem~nt, as described previously.
FIGS. 5A~5C illustrate a prPferrPd embodiment oP
base member 22 which is used to connect the distal end of tr~n.~;tter 14 to flexible conn~ctor 20. The base member provides additional stiffness and provides connections which are selected to be located at a stress node of transmitter 14. Hence, it is desirable to ~i"im;ze the overall leng~h of th~ base member and thereby minimize stiffness and maintain the connections at the stress node. A~ shown in FIG. 5A, the length of the base member is sufficient simply to pro~ide good coupling to the distal segmen~ 16b and good coupling to the proximal ends of wires 50a-50d.
Accordingly, a central recess 92 extends from ~he proximal end of ba~e member 22 (seen in FIG. 5C, which is a view taken along line~ C-C) by a length which is approximately equal to the length of distal segment 16b of transmitter 14.
It is seen that tha diameter of recess 92 is equal to D2, ~ which is the diameter of the distal segment 16b (shown in : 20 FIG. ~A).
~: At the distal end of the base member, as shown in : :FIG. 5B, which is a distal end ~iew taken along se~tion : lines B-B, wire re esses 94a-94d are provided, each of a diameter D3, which is the diameter of each of wires 50a-50d.
It is appreciated that wires 50a-50d are adhesively secured : in wire recesses 94a-94d; and distal segment 16b of t~ansmitt&r 14 likewise is adhesively secured wi~hin recess 92. If desired, other means for affixing the wires and the di~tal segment to base r~rh~r 22 may be used, su¢h as those 30 ~ means known to t~ose of ordinary skill in the art when interconnecting ultrasonic devices.
Base member 22, which is seen to be cylindrical, pre~erably i5 formed of the same material as transmitter 14.
Thus, the base ~nemb~r is formed o~ a high ~ch~nical Q
35 material, preIerably alumirlum or aluminum alloy. ~ec~ss~
92 and 94a-94d are machin2d into a solid cylindric:al segment, thus resulting in the illustrated ba~e memberO
A pref erred embo~l i ment of tip 18, which has been ~s~rib d above, i~ illustrated in FIGS. 6A and 6B, wherein 2 ' ~ 3 WO93/16~6 -27- ~CT~US93/00764 FIG. 6B is a plan view of proximal portion 68 and FIG. 6A is a partial sectional diagram taken along lines A-A of FIG.
6B. Here, the tip is configured to enhance cavitation, althou~h other designs that produce incidental cavitation can be used with the ultrasonic transmission apparatus of the present invention for different applications. It is seen that distal portion 66 includes a truncated semi-spheroid shape 74; and the distal portion and proximal portion 68 both are cylindrical. Intermediate portion 74, whose thickness is less than the diameter of either th~ .
distal portion or the proximal portion, is provided as a connecting m~rher therebetween. As a result, the exterior surface of the tip undergoes a discontinuity defined by the : intermediate portion, resulting in a cavitation surface 72 on proximal portion 68 and a cavitation surface 78 on distal portion 66. It is seen that each of these cavitation surfaces is substantially perpendicular to longitudinal axis 102 ~f tip 18.
~ The tip includes a center bore 104 which extends : 20 throu~h the distal, intermediate and proxim~l portions thereof and is adapted to receive aforede~cribed guide wire conduit 56 or to serve as a conduit for guide wire 58 ~not sh~wn3. As also shown in FIGS. 6A and ~B, proximal portion .
: : 68 i~ provided with recesses 76a-76d to receive wires 50a-25~ 50d,~respectively, of flexible connector 20. As these wires ~; undergo ultrasonic di~plac~ment in the direction of longitudinal axis 102, tip 18 is driven at the sam~
ultrasoni~ frequency to produce cavitation in the patient's : bl:ood v~ssel, or in any other fluid in which the ultrasonic ~: 30 tran~mission apparatus is disposed. Preferab~y, the tip is .~ driven at an ultrasonic frequency in the range of about 40 ~Hz to 60 kHz because this frequency permit~ the tîp to be r2ciprocally~driven with a displacement in the range of 20~ ~o 60~ peak-to-peak without signi~icant attenuation in *lexible conn~ctor 20 due to sharp h~nA~ therein as tra~smitt¢r 14 follows such bends in the patient's ~lood ~e~C~l~ Additionally, the tip may be driven by operating energy source 88 (FIG. 4) in a pulsed mode to prevent the WO93/16646 2 :L ~ 28 PCT/UIS93/007 accumulation of, for example, fibrin particles in tip 18 when a thrombus is destroyed.
FIG. 6C illustrates a modified version of the tip shown in FIGS. 6A and 6B, in which the distal por~ion is substantially cylindrical and includes a concave face 80 whirh serves as yet an additional cavitation surface.
~ IGS. 7A-7K illustrate other embodiments of tip 18 which provide sufficient cavitation when the tip is driven at ult-~sonic frequencies, whereby a thrombus is destroyed, FIG. 7A illustrates a so called reverse mushroom shape, wherein the front face of the tip is substantially planar, and the proximal portion thereof is semi-spheroid in shape.
FIG. 7B illustrates a mushroom shape lO~, which is seen to be the inverse, or complement, of reverse mushroom shape 106 of FIG. 7A.
FIG, 7C illustrates a double mushroom shape 110, wherein the embodiments of FI~S. 7A and 7B are interconnected by an intermediate portio~ to provide two cavitation surfaces similar to aforedescribed cavitation sur~ce~ 72 and 78 of FIG. 6A.
FIG. 7D illustrates ancther emboAir~nt of a doub~e : :mushro~m shape wherein a distal s~mi-spheroid shape 112 is .
coupled to a~ opposltely disposed semi-spheroid shape by an int~rmediat~ section 116.
:~ 25 FIG. 7E, which is taken along section lines E-E of FIG. 7D shows that the ~hickness of interm2diate section 116 is less than the diameter o~, for ~Y~rle, distal semi-:spheroid shape 112. In this configuration, two cavitation surfaces 113 and 114 are provided on the distal and pro~imAl sections, respectively. The e~fect of the tip configuration shown in FIGS. 7D and 7E is substantially the same as that :
of.the tip configur~tion ~hown in FIG. 6A.
FIG. 7F illustrates a doub~e mushroom configuration having a mushroom-shaped distal ssction 118 ~5 and ~ mu~hroom-shaped proximal section 122 with an -:
intexmediate section 120 disposed therebetweenO The.
intermedia~e section may be disk-shaped and a center post 124 is used to connect distal s~ction 118, inte~m~di~te section 120 and proximal section 122, as illustr~ted. In WO93/16646 -29- ~1 2 3 D a 6 PCT/US93/~0764 the configuration shown in FIG. 7F, four cavitation surfaces are provided, one on distal section 118, one on proximal se~tion 122 and two on intermediate section 120.
FI~S. 7G-7I illustrate yet another embodiment of tip 18, wherein a distal section 126 that is substantially mushroom~shaped is connected to a distal cavitation portion 132 by means of a con~ecting section 130. FIG. 7I, which is taken along section lines I~I in FI~. 7G, illustrates connecting section 130 as a relatively thin web whose thickness is less than the diameter of distal section 126, and FIG. 7I ~urther illustrates that distal cavitation portion 132 is substantially disk-shaped. It is seen that a cavitation surface 128 is provided on distal section 126 and a cavitation surface 129 is provided on distal cavitation portion 132.
Distal cavitation portion 132 is coupled~to a reverse mushroom-shaped proximal section 138 by meAn~ of an int~rmediate section 134, which is shown in approximate proportion in FIGo 7H, taken along section lines H-H of FIG.
7G. It is seen that intermediate section 134 is a rel;atively thin web similar to the thin web of connecting : section 130, and rotated by about 90~ with respe~t thereto.
Tha thickness of intermediate section 134 is less than the diameter of proximal section 138. ~ccordi~gly, caYitation ~urfac~ ~36 is provided on proximal section 138 and a ca~:i~ation surf ac:s 13 5 is provided c~n d istal ~avitativn ~: portion 132 in facing relation thereto. In the em~odim~nt shown in FIGS. 7G-7I, four c~vita~ion surfaces are provided, one on dis~al sec:tion 12 6, two on di~tal ca~ritation portion î~2 and one on proximal section 138~ The cavitati~ effect produced by th~ tip shown in FIGS . 7G-7I i~ substantially similar to the cavitation effect produced l~y the tip shown in ~IG. 7F.
FIG. 7J illustrates yet another e~bodi~ent of a tip ha~ving an incrP~r~ urface for prod~ ing c:avita~ion.
Here, the tip is hown as an elongated s~mi sph~ro7 d shape 140 ha~ing a no~ch 142 in the central portion thereof, r~sulting in a discontinuity in the exterior surf ~ce to de~ine cavitation surfaces 144 and 146. FIG. 7K is taken W~93/16~6 2 l .~ 8 0 ~ i~ ~30- PCT~US93~0~7~

along section lines K-K of FIG. 7J and illustrates the shape of cavitation surface 146. It will be apprecia~ed that cavitation surface 144 is substantially similar in shape.
Tests have been conducted on the preferred embodiment of the presPnt invention which confirm the improved results attained thereby. These tests, based upon the embodiment illustrated in FIGS. l, 2, 4 and 6, are s~mmarized as follows:
DISPLACEMENT
Transmitter 14, connector 20 and tip 18 were inserted into an anatomic model leading to the left anterior descending (LAD~ coronary artery. Puncture site was at the femoral artery and tip 18 reached the LAD by way of a 9-French Judkins left coronary guide ratheter. Tip : 15 displa¢ement was obser~ed and measured by conventisnal video magnification, with the following results:
In~ut Power Displacement (microns~ -8 watts 17.2 peak-to-peak 20.0 ~ ~ 20 ~2 2~7 : ~ ~' 14 31.5 38.
DISPL~CEMENT COMPARISON -~
~ 25 A c~mparison of the displacement at~ained by th~ ;
;~; : ultrasonic transmission apparatus of the present invention with apparatus of the type described in Applica~ion Serial N~ 44~465 was conducted. The embodiment of the present ~ inYention waC 126cm in overall length, and tran~mitter 14~ ~ 30 w~s formed with four horn segments dis~ributed along its l~ngth and interspersed with straight se~men~sO The diameter Dl of the transmitter at its proximal end was l.
mm and the diameter D2 ~ the transmitter at its dis~al end wa~ 0.5mm. ~he apparatus to which the presQnt invention was c~mpared was formed of a wir~ l25.5cm long of constant, uni~orm diameter of 0.5mm along its entire length ~referred : to herein as the "straight wire tran~mitter'l~. Both transmitters were coupled to-horns ~such as horn l2) of substantially the same profile and both ~r~-e~;~ters were WO 93/16646 -3 1- PCr/US93/00764 energized at about 28 . 5 k~z . A mod~l A-200A Branson Horn Analyzer was used for testing.
No Bend: When both transmitters were testsd at the same input power levels in a str~ight water tank having no bend imparted to the transmitter, the tip displacement of the present invention was measured at 65.8~ and the tip displacement of the straight wire transmitter was measured at 11.4~, only 17~ of the displacement attained by the present inv ntion.
Bend: The two transmitters were disposed (one at a time) in a plastic tube bent by 180~ t~ form a curve whose diameter was 9cm; and the plastic tubes were lo~ated in the aforementioned water tank~ Tip displacement of the present invention subjected to this bend was measured at 42.9~ and tip displacement of the straight wire transmitter was measured at less than 2.S~, Thus, by reason of the bend in the tr~n~ritters~ tip displacement is reduced, but this ~: reduction i~ only about 34% of no-bend displacement for the present invention as compared to about 75~ for the straight ~ire transmitter.
FlexibilitY: T~e flexibility of the tip connectPd to tr~itter l~ by connector 20 of the present inv~ntion was ~compared to the flexibility of the tip of the straight : wire transmitter by mea~uring the force naeded to d ~lect the~tip by lmm. For this comparison ~he tr~n~;tter was clamped near its distal end such that the di~tance ~rom the ~-clamp to ~he center of gravity of the tip was 1.3 cm. In : the pre~ent invention, the connector was formed of ~our : ti~anium wires, ~ach of 0.25mm diameter and the straight~ 30 wire transmitter had a diameter of 0.5mm. In both transmit~ers, the cross-sectional areas ~that is, ~he cross-sectional area of th four titanium wir~s and the cross-sectional area o~ the straight wire transmitter) were 0,196mm2. The h~n~; ng force needed to achleve a lmm ip defl~ction o~ the present invention was 7 grams and the b~n~in~ fQrce nePded to achieve a lmm tip deflection of the s~raight wire transmitter was 35 grams.

W093/l~S 21 2 ~ ~ a 6 -32- pcT/us~3/no7~4 THROMBOLYSIS
Thrombolysis efficacy of the ultrasonic transmission apparatus was tested empirically on samples of bovine ~hrombus placed in the ~AD. Thrombolysis commenced with input power set at 12 watts and became more consistent once this input power reached 14 watts. The time needed for the apparatus to clear a lesion vari~d with different thrombus samples from about 5 seconds to more than 60 seconds. The ef~ect of drawing the thrombus to tip 18 was clearly observed, even with flow in the LAD of about 10 to 20 ml/min.
S~MM~Y
While the present inv2ntion has been particularly shown an~ described with reference to pref rred embo~i~ents, it will be readîly appreciated that various changes may be made without departing from the spirit and scope of,the : invention. For example, the tips shown in ~IGS. 7A-7K may be provided with a concave face at the distal end thereo~.
;~ In addition, although several examples of tip configurations ~0 ~have ~een shown and described herein, it will be recognized ~: that oth r configurations may be used, if desired. It i~
preferred, however, that the tip pYh;hit an increase in ~ur~ace area so~as to provide optimum cavitation for destroying thrombi. Nevertheless, in different applications 25 ~ of the present inven~ion, the tip will be configured so as not to generate substantial cavitation.
It is inten~e~ that the appended ~laims be i~t~rpreted as covering the embo~irents disclosed herein, those vari~tions and changes which have been ~iscussed above, and all ~quivalents theretoO
i , . .. .

Claims (53)

WHAT IS CLAIMED IS:

1. Ultrasonic transmission apparatus comprising:
a horn connectable to an energy source for amplifying ultrasound displacement;
transmission means formed of material having relatively high mechanical Q for transmitting ultrasonic energy therethrough at a frequency f and comprised of multiple horn segments distributed longitudinally along said transmission means, each horn segment having a length substantially equal to a multiple of .lambda./2, where .lambda. - c/f (c is the speed of sound in said material), the transmission means having a proximal end of cross-sectional diameter D1 connected to said horn and a distal end of cross-sectional diameter D2, where D1 > D2;
a tip driven by said ultrasonic energy; and flexible means for transmitting ultrasonic energy therethrough and having a first end connected to the distal end of said transmission means and a second end connected to said tip for transferring to said tip ultrasonic energy received from said transmission means.

2. The apparatus of Claim 1 wherein said flexible means is comprised of plural wires, each of a diameter less than D2.

3. The apparatus of Claim 2 wherein said flexible means further includes means for isolating each of said plural wires.

4. The apparatus of Claim 3 further including a base member for coupling the first ends of said plural wires to said distal end of said transmission means.

5. The apparatus of Claim 4 wherein said base member has a length Lb, said flexible connector means has a length L and said tip has a length Lt and L+Lb+Lt = k .lambda.'/2, where k is an integer, .lambda.' = c'/f, c' is the effective speed of sound through said base member, said flexible connector means and said tip, and f is the frequency of said ultrasonic energy.

6. The apparatus of Claim 4 wherein said base member comprises a generally cylindrical housing having a central recess of diameter substantially equal to D2 open at one end of said housing for receiving said distal end of said transmission means, and plural recesses open at an opposite end of said housing for receiving the first ends of said plural wires.

7. The apparatus of Claim 2 wherein each of the wires of said flexible means is formed of material having a tensile strength different than that of the material of said transmission means.

8. The apparatus of Claim 3 wherein said means for isolating each of said plural wires comprises tubular channel means disposed about said wires.

9. The apparatus of Claim 8 wherein said tubular channel means is comprised of plural flexible tubes, each disposed about a respective wire.

10. The apparatus of Claim 8 wherein said transmission means is further comprised of straight segments interspersed with said horn segments, each straight segment having a length substantially equal to a multiple of .lambda./2.

11. The apparatus of Claim 10 wherein said transmission means further comprises a sleeve disposed about at least those horn and straight segments expected to be inserted in a lumen with which said apparatus is used, said sleeve having a proximal end portion and a distal end portion secured to said tubular channel means.

12. The apparatus of Claim 11 wherein said sleeve is formed of flexible material and has an inner diameter which, at any longitudinal location thereof, is greater than the diameter of said transmission means at the same longitudinal location.

13. The apparatus of Claim 11 wherein said tubular channel means has a distal end spaced from said tip and open to permit fluid to flow through said tubular channel means.

14. The apparatus of Claim 13 wherein said sleeve has an inner diameter spaced from said transmission means to define a fluid channel; and further comprising fluid supply means for supplying fluid through said fluid channel to said tubular channel means to provide a lubricant for and to reduce the transverse vibration of said transmission means.

15. The apparatus of Claim 14 wherein said fluid supply means comprises an input conduit coupled to said sleeve in the vicinity of said proximal end portion thereof for coupling fluid thereto, and valve means in fluid communication with said proximal end portion of said sleeve to prevent backflow of fluid through said sleeve.

16. The apparatus of Claim 15 wherein said fluid supply means further includes a coupling channel for coupling said proximal end portion of said sleeve to said horn, and wherein said valve means comprises a manually tightened cap disposed over said coupling channel and said horn and operable to seal an O-ring at a node of longitudinal ultrasonic vibration.

17. The apparatus of Claim 16 wherein said horn is provided with a pair of annular shoulders at said node of longitudinal ultrasonic vibration to define the location of said O-ring.

18. The apparatus of Claim 14 further including a protective sheath coupled in fluid tight relation to said sleeve and disposed over at least one segment at the proximal end of said transmission means to enable a user to grasp said proximal end when guiding said transmission means into the lumen without substantially damping ultrasonic vibrations of said transmission means.

19. The apparatus of Claim 18 wherein said at least one segment over which said protective sheath is disposed is provided with plural annular shoulders located at nodes of ultrasonic vibration to contact said sheath in the event said sheath is deformed; said sheath having an inner diameter spaced from said transmission means to define a fluid conduit in fluid communication with the fluid channel of said sleeve.

20. The apparatus of Claim 19 wherein said means for supplying fluid to said channel is coupled to said protective sheath; and wherein said fluid additionally prevents backflow through said tubular channel means and said fluid channel to said fluid conduit.

21. The apparatus of Claim 1 wherein said horn segments are distributed substantially regularly along said transmission means.

22. The apparatus of Claim 21 wherein said transmission means includes straight segments each of a length that is a multiple of .lambda./2 and interspersed with said horn segments, the transmission means further including a protective sheath disposed over at least one segment at the proximal end of said transmission means and formed of relatively rigid material which, when grasped by a user, does not deform into contact with said transmission means and thereby damp ultrasonic vibrations thereof.

23. The apparatus of Claim 22 wherein the protective sheath has a distal end located substantially at a node of ultrasonic vibration in said transmission means.

24. The apparatus of Claim 2 wherein said transmission means is formed of aluminum and the wires of said flexible connection means are formed of titanium.

25. The apparatus of Claim 24 wherein said horn and transmission means are of unitary construction.

26. The apparatus of Claim 1 wherein said tip is configured to enhance cavitation in a fluid.

27. The apparatus of Claim 26 wherein said tip is comprised of proximal and distal portions having respective diameters and interconnected by an intermediate portion having a thickness less than the diameter of each of said proximal and distal portions, said proximal, intermediate and distal portions having a common longitudinal axis.

28. The apparatus of Claim 27 wherein said proximal, distal and intermediate portions are of unitary construction and said flexible connection means is secured to said proximal portion.

29. The apparatus of Claim 27 wherein said distal portion is of substantially truncated semi-spheroid shape and said proximal portion is of cylindrical shape.

30. The apparatus of Claim 27 wherein said distal and proximal portions both are of cylindrical shape.

31. The apparatus of Claim 30 wherein said distal portion has a concave-shaped face.

32. The apparatus of Claim 27 wherein said proximal, intermediate and distal portions have a common longitudinal channel to receive a guide wire for guiding said tip, and thereby said flexible means and said transmission means, through a lumen.

33. The apparatus of claim 32 wherein said flexible means includes a center channel in communication with said common longitudinal channel for receiving said guide wire.

34. The apparatus of Claim 33 further comprising a central guide wire conduit disposed in said common longitudinal channel and said center channel for guiding said guide wire through said tip and through said flexible means.

35. The apparatus of Claim 27 wherein the diameter of the proximal portion is substantially equal to the diameter of the distal portion.

36. The apparatus of Claim 1 wherein said transmission means includes straight segments separating said horn segments, each straight segment having a length substantially equal to a multiple of .lambda./2.

37. The apparatus of Claim 36 wherein the length of a straight segment disposed between successive horn segments differs from the length of either of said successive horn segments.

38. The apparatus of Claim 36 wherein each horn segment has a distal end diameter less than its proximal end diameter.

39. The apparatus of Claim 36 wherein the horn segments are distributed substantially uniformly along said transmission means.

40. Ultrasonic transmission apparatus comprising:
an input horn connectable to an energy source for amplifying ultrasound displacement;
a horn-shaped transmitter formed of material having relatively high mechanical Q for transmitting ultrasonic energy therethrough at a frequency f and having a length substantially equal to a multiple of .lambda./2, where .lambda. =
c/f (c is the speed of sound in said material), the horn-shaped transmitter having a proximal end of cross-sectional diameter D1, connected to said input horn and a distal end of cross-sectional diameter D2, wherein D1 > D2;
a tip driven by said ultrasonic energy; and flexible means for transmitting ultrasonic energy therethrough and having a first end connected to the distal end of said horn-shaped transmitter and a second end connected to said tip for transferring to said tip ultrasonic energy received from said horn-shaped transmitter, said flexible means being comprised of plural wires, each of a diameter less than D2.

41. The apparatus of Claim 40 wherein said flexible means includes means for isolating each of said plural wires.

42. The apparatus of Claim 41 wherein each of said wires is formed of material having a tensile strength different than that of the material of said horn-shaped transmitter.

43. The apparatus of Claim 42 wherein said means for isolating each of said plural wires comprises tubular channel means disposed about said wires.

44. The apparatus of Claim 43 wherein said tubular channel means is comprised of plural flexible tubes, each disposed about a respective wire.

45. The apparatus of Claim 43 wherein at least a portion of said horn-shaped transmitter is disposed in a sleeve, the sleeve being formed of flexible material and having a distal end portion secured to said tubular channel means and a proximal end portion.

46. The apparatus of Claim 45 wherein said tubular channel means has a distal end spaced from said tip and open to permit fluid to flow through said tubular channel means.

47. The apparatus of Claim 46 further comprising fluid supply means for supplying fluid through said sleeve to said tubular channel means to provide a lubricant for and to reduce transverse vibration of said horn-shaped transmitter.

48. The apparatus of Claim 47 further including a protective sheath coupled in fluid tight relation to said sleeve and disposed over a proximal portion of said horn-shaped transmitter to enable a user to grasp said proximal portion when guiding the transmitter into a lumen without substantially damping ultrasonic vibrations of said transmitter.

49. The apparatus of Claim 48 wherein said protective sheath, said sleeve and said tubular channel means comprise a fluid conduit from said fluid supply means to said tip; and wherein said fluid additionally prevents backflow through said fluid conduit.

50. The apparatus of Claim 40 wherein the horn-shaped transmitter is formed of aluminum and the wires of said flexible connector means are formed of titanium.

51. A tip for use in ultrasonic transmission apparatus driven for longitudinal, reciprocating displacement, comprising a proximal portion connectable to an ultrasonic transmitter, a distal portion and an intermediate portion connecting said proximal and distal portions, the proximal and distal portions having respective diameters and the intermediate portion having a thickness less than the diameter of each of said proximal and distal portions, said proximal, distal and intermediate portions having a common longitudinal axis, said distal portion being of substantially truncated semi-spheroid shape having a flat front face and said proximal portion being of cylindrical shape.

52. A tip for use in ultrasonic transmission apparatus driven for longitudinal, reciprocating displacement, comprising a proximal portion connectable to an ultrasonic transmitter, a distal portion and an intermediate portion connecting said proximal and distal portions, the proximal and distal portions having respective diameters and the intermediate portion having a thickness less than the diameter of each of said proximal and distal portions, said proximal, distal and intermediate portions having a common longitudinal axis, said distal portion being mushroom-shaped and said proximal portion being reverse mushroom-shaped.

53. A tip for use in ultrasonic transmission apparatus driven for longitudinal, reciprocating displacement, comprising a proximal portion connectable to an ultrasonic transmitter, a distal portion and an intermediate portion connecting said proximal and distal portions, the proximal and distal portions having respective diameters and the intermediate portion having a thickness less than the diameter of each of said proximal and distal portions, said proximal, distal and intermediate portion having a common longitudinal axis, and a disk-shaped intermediate section secured to said intermediate portion and disposed between said distal and proximal portions.