Acousting imaging catheters and the like

Acoustic imaging balloon catheters formed by a disposable liquid-confining sheath supporting a high fidelity, flexible drive shaft which carries on its end an ultrasound transducer and includes an inflatable dilatation balloon. The shaft and transducer rotate with sufficient speed and fidelity to produce real time images on a T.V. screen. In preferred embodiments, special features that contribute to the high fidelity of the drive shaft include the particular multi-filar construction of concentric, oppositely wound, interfering coils, a pre-loaded torque condition on the coils enhancing their interfering contact, and dynamic loading of the distal end of the probe, preferably with viscous drag. The coil rotating in the presence of liquid in the sheath is used to produce a desirable pressure in the region of the transducer. Numerous selectable catheter sheaths are shown including a sheath with an integral acoustically-transparent window, sheaths with end extensions that aid in positioning, a liquid injection-producing sheath, a sheath having its window section under tension employing an axially loaded bearing, a sheath carrying a dilatation or positioning balloon over the transducer, a sheath carrying a distal rotating surgical tool and a sheath used in conjunction with a side-viewing trocar.

BACKGROUND OF THE INVENTION 
This invention relates to acoustic imaging catheters employing a rotating 
transducer. 
It has long been recognized that acoustic imaging by use of internal probes 
has potential use in visualizing conditions of a body. 
Wider effective use of acoustic imaging would occur, especially in the 
vascular system, if such a system could be considerably smaller, have good 
image fidelity, and be simple, inexpensive and dependable. 
SUMMARY OF THE INVENTION 
An acoustic catheter is provided comprising an elongated, flexible, 
liquid-confining catheter sheath and an elongated, flexible ultrasonic 
probe disposed within and rotatably supported by a lumen of the sheath, 
the ultrasonic probe comprising a transducer supported on the end of an 
elongated coil-form drive shaft, a distal portion of the catheter sheath 
that corresponds with the position of the transducer being substantially 
transparent to acoustical energy transmitted and received by the 
transducer and the probe, and the sheath being cooperatively constructed 
and arranged to enable removal and replacement of the sheath in a 
disposable manner. 
In preferred embodiments, the sheath includes a catheter sheath having a 
distal projection supported by the catheter sheath and extending distally 
from the position of the transducer; the distal projection includes an 
elongated guide means of smaller diameter and greater flexibility than the 
catheter sheath; alternatively, the distal projection includes means to 
introduce contrast medium or other fluid distal of the probe. 
In preferred embodiments, the portion of the catheter sheath which is 
substantially transparent to acoustical energy is integral (i.e. without a 
joint) with a proximal portion of the catheter sheath; the substantially 
transparent portion of the catheter sheath has a thinner wall than said 
proximal portion; and the catheter sheath includes a resinous substance. 
Another preferred embodiment includes the elongated probe or catheter 
described above, in combination with a hollow trocar adapted to receive 
the probe or catheter, the trocar having a side-facing window adapted to 
register with the transducer enabling the transducer to form acoustic 
images of tissue into which the trocar has been forced. 
Other aspects, features and advantages of the invention will be apparent 
from the following description of the preferred embodiments and from the 
claims. 
The invention enables the achievement of micro-acoustic, close-up imaging, 
via catheter, of restricted regions of the body that are difficult of 
access.

GENERAL STRUCTURE 
Referring to FIG. 1, a micro-acoustic imaging catheter 6 according to the 
invention is driven and monitored by a control system 8. The catheter is 
comprised of a disposable catheter sheath 12 (FIGS. 2 and 4) having a 
sound-transparent distal window 24 provided by dome element 25 (FIG. 4), 
in which is disposed a miniature, rotatable ultrasonic transducer 10 
(FIGS. 3 and 4) driven by a special, high fidelity flexible drive shaft 
18. A relatively rigid connector 11 is joined to the proximal end of the 
main body of the catheter sheath, adapted to be joined to a mating 
connector of drive and control system 8. 
The catheter is adapted to be positioned in the body by standard catheter 
procedures for example within a blood vessel or the heart by guiding the 
flexible catheter through various blood vessels along a circuitous path, 
starting, for example, by percutaneous introduction through an introducer 
sheath 13 disposed in a perforation of the femoral artery 15. 
Referring to FIG. 2, disposable catheter sheath 12 is a long tube, extruded 
from standard catheter materials, here nylon, e.g. with outer diameter, D, 
of 2 mm, wall thickness of 0.25 mm and length of 1 meter. Dome element 25, 
connected to the distal end of the tube, is a semi-spherically-ended 
cylindrical transducer cover constructed of material which is transparent 
to sound waves, here high impact polystyrene. This dome element has a 
thickness of approximately 0.125 mm and a length E of about 8 mm. For 
purposes described later herein, catheter sheath 12 in its distal region 
preferably tapers down over region R as shown in FIG. 4 to a narrowed 
diameter D' at its distal end, achieved by controlled heating and drawing 
of this portion of the original tube from which the sheath is formed. 
Catheter sheath 12 and acoustically transparent dome element 25 are 
adhesively bonded together. 
Referring to FIGS. 3 and 4, the drive shaft assembly 18 is formed of a pair 
of closely wound multi-filar coils 26, 28 wound in opposite helical 
directions. These coils are each formed of four circular cross-sectional 
wires, one of which, 30, is shown by shading. Coils 26, 28 are soldered 
together at both the distal and proximal ends of the assembly in 
interference contact, here under rotational pre-stress. By also providing 
a pitch angle of greater than about 20.degree., a substantial part of the 
stress applied to the wire filaments of the coil is compression or tension 
in the direction of the axis of the filaments, with attendant reduction of 
bending tendencies that can affect fidelity of movement. There is also 
provision to apply a torsional load to the distal end of the assembly to 
cause the drive shaft to operate in the torsionally stiff region of its 
torsional spring constant curve, achieved by viscous drag applied to the 
rotating assembly by liquid filling the narrowed distal end of the 
catheter sheath (FIG. 4). Such loading, together with initial tight 
association of the closely wound filaments in the concentric coils, 
provides the assembly with a particularly high torsional spring constant 
when twisted in a predetermined direction. Thus, despite its lateral 
flexibility, needed for negotiating tortuous passages, the assembly 
provides such a torsionally stiff and accurate drive shaft that rotary 
position information for the distal end can, with considerable accuracy, 
be derived from measurement at the proximal end of the drive shaft, 
enabling high quality real-time images to be produced. (Further 
description of the coils of the drive shaft and their condition of 
operation is provided below.) 
Coaxial cable 32 within coils 26, 28 has low power loss and comprises an 
outer insulator layer 34, a braided shield 36, a second insulator layer 
38, and a center conductor 40. Shield 36 and center conductor 40 are 
electrically connected by wires 42, 44 (FIG. 5) to piezoelectric crystal 
46 and electrically conductive, acoustical backing 48 respectively, of the 
transducer. Helical coils 26, 28, especially when covered with a highly 
conductive metal layer, act as an additional electric shield around cable 
32. 
Transducer crystal 46 is formed in known manner of one of a family of 
ceramic materials, such as barium titanates, lead zirconate titanates, 
lead metaniobates, and PVDFs, that is capable of transforming pressure 
distortions on its surface to electrical voltages and vice versa. 
Transducer assembly 10 is further provided with an acoustic lens 52. The 
radius of curvature B of lens surface 52 is greater than about 2.5 mm, 
chosen to provide focus over the range f (FIG. 6) between about 2 to 7 mm. 
The lens is positioned at an acute angle to the longitudinal axis of the 
catheter so that, during rotation, it scans a conical surface from the 
transducing tip, the angle preferably being between 10.degree. and 
80.degree., e.g., 30.degree.. Transducer backing 48 is acoustically 
matched to the transducer element to improve axial resolution. 
The transducer assembly 10 is supported at the distal end of the drive 
shaft by a tubular sleeve 29 which is telescopically received over a 
distal extension of the inner coil 28, as shown in FIG. 3. 
Referring again to FIG. 4, the length, E, of dome element 25 is sufficient 
to provide headroom F for longitudinal movement of transducer 10 within 
the dome element as catheter sheath 12 and coils 26, 28 are twisted along 
the blood vessels of the body. In the untwisted state, transducer 10 is a 
distance F, about 2 to 3 mm, from the internal end surface of the dome 
element 25. The dome element, along with catheter sheath 12 is adapted to 
be filled with lubricating and sound-transmitting fluid. 
FIGS. 7-7b show the filling procedure used to prepare ultrasound catheter 
sheath 12 (or any of the other interchangeable sheaths, see FIGS. 13-26) 
for attachment to the ultrasound imaging drive shaft and transducer 
assembly. A sterile, flexible filling tube 17 attached to a syringe 19 is 
filled with sterile water. This filling catheter is inserted into the 
ultrasound catheter sheath 12, all the way to the distal tip. The water is 
then injected until it completely fills and the excess spills out of the 
ultrasound catheter while held in a vertical position; see FIG. 7a. This 
expels air from the catheter which could impair good acoustic imaging. 
Continued pressure on the plunger of the syringe causes the flexible tube 
17 to be pushed upward, out of catheter 12, FIG. 7b, leaving no air gaps 
behind. This eliminates the necessity to carefully withdraw the flexible 
filling tube at a controlled rate which could be subject to error. A 
holding bracket 21 is used to hold the catheter vertical during this 
procedure. 
After the catheter sheath 12 is filled, the acoustic transducer 10 and 
shaft 18 are inserted, displacing water from the sheath 12, until the 
installed position, FIG. 7d, is achieved. 
FIGS. 8 and 8a (and FIG. 1, diagrammatically) show the interconnection 
arrangement for a connector 7 at proximal end of the acoustic catheter 
with connector 16 of the driving motor 20, and the path of the electric 
wires through the center shaft 43 of the driving motor. The center shaft 
and connector 16 rotate together, as do the wires that pass through the 
hollow motor shaft. The latter connect to a rotating electrical joint 27, 
which is held stationary at the back end and is connected to stationary 
coaxial cable 45 through a suitable connector such as a common BNC type. 
The enlarged view shows how the motor connector 16 and the driveshaft 
connector 7 mate when the two assemblies are pushed together, thereby 
making both electrical and mechanical contact. The catheter connector 7 is 
held in position by an ordinary ball bearing which provides a thrusting 
surface for the rotating connector 16 and driveshaft 18 while allowing 
free rotation. The disposable catheter sheath 12 includes an inexpensive, 
relatively rigid hollow bushing 11 of cylindrical construction that allows 
it to be slid into and held by means of a set screw in the housing that 
captures the non-disposable bearing, connector, and driveshaft 18. Drive 
shaft coil assembly 18, thus attached at its proximal end to connector 16 
of drive motor 20, rotates transducer 10 at speeds of about 1800 rpm. The 
transducer 10 is electrically connected by coaxial cable 32 extending 
through coil assembly 18 and via the cable through the motor to the 
proximal electronic components 22 which send, receive and interpret 
signals from the transducer. Components 22 include a cathode ray tube 23, 
electronic controls for the rotary repetition rate, and standard 
ultrasonic imaging equipment; and see FIG. 12. A rotation detector, in the 
form of a shaft encoder shown diagrammatically at 19, detects the 
instantaneous rotational position of this proximal rotating assembly and 
applies that positional information to components 22, e.g., for use in 
producing the scan image. 
By thus depending upon the position of proximal components to represent the 
instantaneous rotational position of the distal components, the rotational 
fidelity of the drive shaft is of great importance to this embodiment. 
Manufacture and Assembly of the Drive Shaft 
Referring to FIGS. 3 and 4, coils 26, 28 are each manufactured by winding 
four round cross-section stainless steel wires of size about 0.2 mm, so 
that D.sub.o is about 1.3 mm, D.sub.i is about 0.9 mm, d.sub.o is about 
0.9 mm and d.sub.i is about 0.5 mm. The coils are closely wound with a 
pitch angle .alpha..sub.o and .alpha..sub.i where .alpha..sub.o is smaller 
than .alpha..sub.i, e.g., 221/2.degree. and 31.degree., respectively. 
(Flat wires having a cross-sectional depth of about 0.1 mm may also be 
used.) The pitch angles are chosen to eliminate clearances 60 between the 
wires and to apply a substantial part of the stress in either tension or 
compression along the axis of the wire filaments. The coils, connected at 
their ends, are adapted to be turned in the direction tending to make 
outer coil 26 smaller in diameter, and inner coil 28 larger. Thus the two 
assemblies interfere with each other and the torsional stiffness constant 
in this rotational direction is significantly increased (by a factor of 
about 6) due to the interference. Operation of the driveshaft in the 
torsionally stiff region with enhanced fidelity is found to be obtainable 
by adding a torsional load to the distal end of the rotating assembly of 
catheter. The importance of rotational fidelity and details of how it is 
achieved warrant further discussion. 
For ultrasound imaging systems, the relative position of the ultrasound 
transducer must be accurately known at all times so that the return signal 
can be plotted properly on the display. Any inaccuracy in position 
information will contribute to image distortion and reduced image quality. 
Because, in the preferred embodiment, position information is not measured 
at the distal tip of the catheter, but rather from the drive shaft at the 
proximal end, only with a torsionally stiff and true drive shaft can 
accurate position information and display be obtained. 
Furthermore, it is recognized that any drive shaft within a catheter sheath 
will have a particular angular position which is naturally preferred as a 
result of small asymmetries. Due to this favored position, the shaft 
tends, during a revolution, to store and then release rotational energy, 
causing non uniform rotational velocity. This phenomenon is referred to as 
"mechanical noise" and its effect is referred to as "resultant angular 
infidelity" for the balance of this explanation. 
According to the present invention, use is made of the fact that suitably 
designed concentric coils interfere with each other, as has been mentioned 
previously. When twisted in one direction, the outer layer will tend to 
expand and the inner layer contract thus resulting in a torsional spring 
constant which is equal only to the sum of the spring constants of each of 
the two shafts. When, however, twisted in the opposite direction, the 
outer layer will tend to contract while the inner layer will expand. When 
interference occurs between the inner and outer layers the assembly will 
no longer allow the outer coil to contract or the inner to expand. At this 
point, the torsional spring constant is enhanced by the interference 
between the shafts and the torsional spring constant is found to become 
five or ten times greater than the spring constant in the 
"non-interference" mode. 
Referring to FIG. 9, the relationship between torque and angular deflection 
for such a coil assembly is shown, assuming one end fixed and torque 
applied at the opposite end. `Y` represents mechanical noise; `Z` 
resultant angular infidelity; `T` the interference point; the slope of the 
line `U`, the torsional spring constant (TSC) without interference (i.e., 
the sum of the torsional spring constant of each of the two coils); and 
the slope of the line `V`, the TSC with interference. Thus, TSC is shown 
to increase dramatically at the interference point. 
Referring to FIG. 10, by pre-twisting the shafts relative to one another 
and locking their ends together in a pre-loaded assembly, the interference 
point is moved to be close to the rest angle and resultant angular 
infidelity, Z, is reduced in the given direction of rotation. 
To improve upon this effect even further, dynamic frictional drag is 
intentionally introduced at the distal end of the shaft to raise the level 
of torque being continually applied to the system. This ensures operation 
of the shaft in the region of the high torsional spring constant or 
"interference" mode throughout its length, producing a rotationally 
stiffer shaft. This is shown in FIG. 11, where `W` is dynamic load and `X` 
is the region of operation. The use of such dynamic drag is of particular 
importance in certain catheters of small diameter, e.g. with outer 
diameter less than about 2 mm. 
To form inner coil 28, four individual wires are simultaneously wound 
around a mandrel of about 0.5 mm outer diameter. The free ends of this 
coil are fixed, and then four wires are wound in opposite hand directly 
over this coil to form the outer coil 26. The wires are wound under 
moderate tension, of about 22.5 gm/wire. After winding, the coils are 
released. The inner mandrel, which may be tapered or stepped, or have a 
constant cross-sectional diameter, is then removed. The wire ends are 
finished by grinding. One end is then soldered or epoxied to fix the coils 
together for a distance of less than 3 mm. This end is held in a rigid 
support and the coils are then twisted sufficiently, e.g. 1/2 turn, to 
cause the outer coil to compress and the inner coil to expand, causing the 
coils to interfere. The free ends are then also fixed. 
The coil assembly 18 is generally formed from wires which provide a low 
spring index, that is, the radius of the outer coil 26 musket be not more 
than about 2.5 to 10 times the diameter of the wires used in its 
construction. With a higher index, the inner coil may collapse. The 
multi-filar nature of the coils enables a smaller diameter coil to be 
employed, which is of particular importance for vascular catheters and 
other catheters where small size is important. 
After the coil assembly is completed, coaxial cable 32 is inserted within 
the inner coil. The cable may be silver-coated on braid 36 to enhance 
electrical transmission properties. It is also possible to use the inner 
and outer coils 26, 28 as one of the electrical conductors of this cable, 
e.g. by silver coating the coils. 
Referring back to FIGS. 3 and 5, to form transducer 10, wire 42 is soldered 
to either side of electrically conducting sleeve 29 formed of stainless 
steel. Wire 44 is inserted into a sound absorbent backing 48 which is 
insulated from sleeve 29 by insulator 72. Piezoelectric element 46 of 
thickness about 0.1 mm is fixed to backing 48 by adhesive and electrical 
connection 74 is provided between its surface and the end of sleeve 29. 
Thus, wire 42 is electrically connected to the outer face of piezoelectric 
element 46, and wire 44 electrically connected to its inner face. 
Spherical lens 52, formed of acoustic lens materials is fixed to the outer 
surface of element 46. 
Referring to FIGS. 4 and 7-7d, the completed drive shaft 18 and transducer 
10 are inserted into disposable catheter sheath 12, positioning transducer 
10 within acoustically transparent dome element 25, with liquid filling 
the internal open spaces. The catheter thus prepared is ready to be driven 
by the drive assembly; see FIG. 8. 
During use, rotation of drive shaft 18, due to exposure of the helical 
surface of the outer coil to the liquid, tends to create helical movement 
of the liquid toward the distal end of the sheath. This tends to create 
positive pressure in dome element 25 which reduces the tendency to form 
bubbles caused by out-gassing from the various surfaces in this region. 
As has been mentioned, it is beneficial to provide added drag friction at 
the distal end of the rotating drive shaft 18 to ensure operation in the 
torsionally stiff region of the torsional spring constant curve. It is 
found that this may be done by simply necking down the distal portion of 
the catheter sheath 12, as shown in FIG. 4 to provide a relatively tight 
clearance between the distal portion of the shaft 18 and the inner surface 
of the sheath, to impose the desired degree of viscous drag. As an 
alternative, the dynamic drag may be provided by an internal protrusion in 
catheter sheath 12 to create a slight internal friction against drive 
shaft 18. 
A preferred acoustic catheter is constructed so that it may be preformed 
prior to use by standard methods. Thus, if the investigator wishes to pass 
the catheter through a known tortuous path, e.g., around the aortic arch, 
the catheter can be appropriately shaped prior to insertion. Such 
preformation can include bends of about 1 cm radius and still permit 
satisfactory operation of the drive shaft. 
Electronics 
FIG. 12 is a block diagram of the electronics of a basic analog ultrasound 
imaging system used with the acoustical catheter. The motor controller (D) 
positions the transducer B for the next scan line. The transmit pulser (A) 
drives the ultrasound transducer. The transducer (B) converts the 
electrical energy into acoustic energy and emits a sound wave. The sound 
wave reflects off various interfaces in the region of interest and a 
portion returns to the transducer. The transducer converts the acoustic 
energy back into electrical energy. The receiver (C) takes this wave-form 
and gates out the transmit pulse. The remaining information is processed 
so that signal amplitude is converted to intensity and time from the 
transmit pulse is translated to distance. This brightness and distance 
information is fed into a vector generator/scan converter (E) which along 
with the position information from the motor controller converts the polar 
coordinates to rectangular coordinates for a standard raster monitor (F). 
This process is repeated many thousands of times per second. 
By rotating the transducer at 1800 rpm, repeated sonic sweeps of the area 
around the transducer are made at repetition rate suitable for TV display, 
with plotting based upon the rotary positional information derived from 
the proximal end of the device. In this way a real time ultrasound image 
of a vessel or other structure can be observed. 
We have found that within a blood vessel imaging system a focal point of 
between 1 and 7 mm is suitable and that a frequency of 15 to 40 MHz 
provides good resolution of vessel features in a practical manner. 
Use 
As mentioned above, the acoustical imaging catheter may be introduced by 
standard techniques, preferably by percutaneous insertion, into any 
desired blood vessel. Alternatively, it can be introduced directly into a 
body cavity or body tissue such as an organ. Due to its rotational 
fidelity, the device provides a relatively high quality, real time image 
of blood vessel tissue and allows ready diagnosis of disease states such 
as occlusion or dyskinesia. The acoustic properties of various tissues can 
also be discerned to allow more accurate diagnosis. It is also possible to 
form 3-dimensional images using appropriate computer software and by 
moving the catheter within the blood vessel. The device is also useful in 
angioplasty therapy to determine the nature and geometry of intravascular 
protrusions. This device may be combined with existing optical devices to 
provide a device having an ultrasonic visualizing probe and a laser 
ablating ability. The device may also be used in diagnosis of, e.g., 
esophageal tumors or prostate carcinomas, by passing the catheter through 
the anus, urethra, trachea, or esophagus. The catheter is also useful for 
valvuloplasty by insertion through a cardiac valve. Further, in 
non-medical areas, the device is useful for any inaccessible passages 
which are fluid filled, and thus transmit sound waves. 
Selectable Catheter Sheaths 
A wide variety of novel disposable catheter sheaths can be substituted for 
catheter sheath 12 and used in the system. 
FIG. 13 and 13a show a flexible, disposable catheter sheath 12a that is 
constructed like sheath 12 and has, in addition at its distal tip, a 
floppy guide wire 80 which is useful for guiding the ultrasound device 
through a valve such as of the heart. The guide wire is constructed of a 
closely wound wire coil 82 and an internal safety wire 84 for added 
strength. Wire 84 is welded to the distal tip of coil wire 82 and its 
proximal end is bent over within dome 25 and securely anchored with epoxy 
cement. In another embodiment, the safety wire extends through a separate 
lumen of the catheter sheath to a securing point at the proximal end of 
the catheter. In addition to its guiding function, coil 80, with suitable 
variation of length and stiffness, is useful in supporting and steadying 
the free end of the ultrasound device during axial movement of the 
catheter to improve its imaging capability; see e.g. FIGS. 30-30c. 
FIG. 14 shows sheath 12b having needle 86 securely anchored to the tip, 
useful for impaling a surface, such as that found in the interior of the 
heart, and temporarily anchoring and steadying the ultrasound device in a 
fixed position. In another embodiment, it too can have a safety wire 
extending to a proximal securing point. This acoustic catheter may be 
introduced through an introducing catheter. In another embodiment, the 
needle can be retracted during introduction. 
FIG. 15 shows another flexible, disposable sheath 12c 4that is constructed 
so that the sonolucent (acoustically transparent) portion 24a is spaced 
from the distal end instead of at the end. The extension 12x beyond the 
window 24a may be of the same flexible catheter material as the main body 
of the sheath or of a different, e.g. softer material, and may be either 
open, so that fluids may pass through it, or closed, so that no fluids 
pass through. The distal extension of the catheter sheath can serve to 
stabilize the lateral position of the transducer during axial movement of 
the catheter during imaging. 
FIG. 16 shows a catheter sheath 12d on which is mounted, over the 
transducer area, a dilatation balloon 55 such as is commonly used for 
angioplasty. The balloon is adapted to be pressurized with liquid, such as 
water, through the same lumen that holds the ultrasound imaging device, 
via an inflation opening in the wall of the catheter sheath. This catheter 
is used to open a clogged, stenotic or narrowed passage in the body, while 
simultaneously measuring the progress of the dilatation procedure with the 
ultrasound images. Another embodiment with a suitable balloon may be used 
to center or position the ultrasound device securely within a body passage 
or cavity and maintain its position away from a feature of interest, for 
instance for imaging a wall of the heart. The balloon in its collapsed or 
unpressurized state is easily inserted prior to positioning and may be 
accurately positioned by use of ultrasound imaging during initial 
placement. In other embodiments a separate lumen is provided for inflation 
of the balloon and/or the balloon is spaced from the distal end of the 
catheter. 
Referring to FIG. 17, a plan view of a preferred embodiment of an acoustic 
imaging balloon dilatation catheter system is shown. The system 120 
includes a boot member 122 including a ferrule member 124 at its proximal 
end, constructed to enable electrical and mechanical connection, as 
discussed for example with respect to FIGS. 8-8a, to the acoustic imaging 
control system, as discussed for example with respect to FIG. 1, for 
transmitting rotary power and control signals to the acoustic imaging 
transducer held within the balloon catheter sheath 139 near balloon 140 
and for receiving acoustical image signals from the transducer to enable 
monitoring and control of the dilatation process, as will be further 
described below. The proximal end of the apparatus further includes a seal 
126 (FIG. 17d) which enables intimate but relatively frictionless contact 
with the portion of the rotating drive shaft, and will also be further 
discussed below. 
The catheter apparatus may be sized for use in various body cavities and 
applications such as the coronary arteries, peripheral arteries such as 
the iliac and femoral artery, the extremities, the esophagus, prostate and 
for valvuloplasty. In a preferred embodiment, shown in FIGS. 17-17c which 
may be of use in the peripheral arteries, for example, or the case of a 
dialysis shunt, a 6 F sheath 128 extends a distance of L.sub.1, about 30 
cm from the end of the seal 126 to a "Y" double flare compression fitting 
130. Fitting 130 includes a side arm 132 for introduction of inflation 
fluid such as water or saline by means of a screw syringe 134 for 
inflation of balloon 140 near the distal end of the catheter 139. The side 
arm 130 further includes inner passageways for control wires (not shown) 
within the balloon for controlling a heating means enabling heating of the 
inflation fluid for the purpose of heated balloon angioplasty. The heater 
control wires may be passed, for example, through conduit 136 to heater 
control module 138. 
Extending distally from the compression fitting 130 is catheter body sheath 
139 which has an outer diameter of 4.8 F and extends a distance L.sub.2 
about 92.5 cm to the center of the balloon 140. The catheter may be 
adapted to track a guide wire 152 which passes through a sonolucent saddle 
member 159 beneath the balloon and out of a distal extension 157 of the 
catheter, distal to the balloon. Also distal to the balloon is 
self-sealing septum tip 142 enabling introduction of saline or another 
fluid for purging the balloon of air bubbles that might impair acoustic 
imaging. Such a self-sealing septum is described in U.S. Pat. No. 
5,002,059, the entire contents of which are hereby incorporated by 
reference. The length of the system 120, from the end of the ferrule to 
the center of the balloon is L.sub.3, about 132.5 cm and the length from 
the seal 126 to the center of the balloon is L.sub.4, about 127.7 cm. The 
catheter 139 extends distally from the center of the balloon a distance 
L.sub.5, about 3 cm. The balloon length, L.sub.6, is about 4 cm (inflated 
diameter about 7-8 mm). The extension 157 distal to the balloon is 
L.sub.7, about 1.5 cm. The catheter length is L.sub.8 about 95 cm. 
Referring to FIG. 17a the distal end of the catheter is shown in partial 
cross section with the balloon deflated and inflated (phantom). A rotating 
ultrasound transducer 146 having a coil form drive shaft 141, as discussed 
herein above, is positioned on the central axis A of the catheter sheath 
139 at a position corresponding to the inflatable dilatation balloon 140. 
The catheter sheath 139 forms a sonolucent guide for the transducer 146 
and drive shaft. The catheter sheath is formed of a thin (0.005 to 0.007 
inch) sonolucent material such as polyethylene to provide sufficient 
guidance for the drive shaft and transducer without causing excessive 
attenuation of the ultrasound signal emitted by the transducer. The 
catheter body material, the balloon material, and the guide-wire saddle 
are in general selected to be sonolucent and have an acoustic impedance 
substantially matched to the body fluid, e.g., blood, to which the 
catheter is exposed, to minimize attenuation of the acoustic signals 
emitted and received from the transducer. Polyethylene is advantageous in 
that it has an acoustic impedance that substantially matches blood and 
saline, it is capable of withstanding high dilatation pressures and is 
only slightly elastic, enabling a reliable balloon inflation diameter. An 
advantage of the present system, which allows observation of balloon 
inflation during dilatation, is that balloon materials with some 
elasticity may be employed without danger of over-inflation within a lumen 
since the operator can suspend inflation in response to the acoustic image 
at any time during treatment. It will be understood that the catheter may 
be formed having sonolucent regions corresponding to the location of the 
transducer while the rest of the catheter is not sonolucent, e.g., made of 
thicker material. Fluid communication between the balloon and the catheter 
is provided through port 151 to equalize the fluid pressure encountered 
during dilatation between the balloon and within the catheter to reduce 
the risk of collapse of the typically thin, sonolucent catheter and 
subsequent undesirable binding of the driving shaft which rotates the 
transducer, when the balloon is inflated at relatively high pressures, 
e.g., over 100 psi for balloon angioplasty procedures. 
The dilatation balloon 140 which is preferably polyethylene, as discussed, 
may be mounted at its ends 147, 148 over the guide-wire saddle by, for 
example, melt-sealing. The balloon may also be secured to the saddle by 
clips or the like as conventionally known. Prior to mounting the balloon 
in this area, the catheter is fitted with the sonolucent saddle 159 that 
extends under the area of the balloon and exits distally and proximally 
beyond the ends of the balloon. The saddle enables the use of a thin 
walled single lumen catheter body that is substantially sonolucent. 
Further, the use of single lumen catheters enables smaller catheter sizes 
to be employed, for example, 3 F catheters which can be used in coronary 
arteries. The saddle guide, as shown in cross section in FIG. 17b (taken 
along line 17b-17b of FIG. 17a) and in FIG. 17c, is a tubular member 
disposed over the catheter having a bowed or stretched portion that 
creates a lumen in which the guide wire is placed. The saddle inner lumen 
is of sufficient clearance to allow the catheter to track over a guide 
wire. The saddle ends 154, 155 are angle cut and smooth edged to allow 
ease of entry of and guidance by the guide wire 152. The saddle is 
preferably formed of polyethylene having a wall thickness, T.sub.1, of 
about 0.004 inch. The thickness of the catheter body wall is T.sub.2, and 
is about 0.007 inch. The guide-wire diameter is D.sub.1 about 0.018 inch 
and the drive shaft is of a diameter D.sub.2 of about 0.045 inch. 
Referring back to FIG. 17a the guide wire passes through a side aperture 
153 in the extension 157 of the catheter 139 distal to the balloon, 
through the inner lumen of the extension 157 and a distal aperture 161. As 
indicated, the guide wire is exposed to the body lumen except for its 
passage through the saddle and distal extension of the catheter. The 
saddle may be, for example, disposed around the entire circumference of 
the catheter along a continuous length of the catheter corresponding to 
the length of the balloon in which case a port at a location corresponding 
to the port 151 must be provided in the saddle, or optionally, the saddle 
may be disposed around the entire circumference of the catheter only at 
its proximal and distal ends, and partially about the circumference 
therebetween, enabling free flow from port 151. 
The distal tip of the catheter is fitted with selfsealing septum 158 to 
allow introduction of saline or the fluid distally, forcing air bubbles 
that might impair acoustic imaging and successful balloon inflation 
proximally. Alternately, the septum may be used as an air vent when a 
needle is inserted, allowing the catheter to be filled with fluid from a 
side arm, in which case bubbles and undesirable air may be expelled 
efficiently and completely. The septum is more completely described in 
U.S. Pat. No. 5,002,059, incorporated supra. 
For heating the balloon inflation fluid, annular electrical contacts 143, 
144 inside of balloon 140 are bonded directly to the catheter sheath 139. 
The contacts are positioned on either side of the transducer 146 and are 
spaced apart approximately half the length of the balloon. The spacing 
from the respective ends of the balloon is approximately one fourth the 
length of the balloon, so that the balloon will heat evenly. The contacts 
143 and 144 connect to opposite poles of current-controlled (constant 
current) radiofrequency power supply in the control module 138. The 
catheter also includes a thermistor 145, located just proximally of the 
transducer 146 for measurements of balloon temperature. Wires for the 
contacts and thermistor (not shown) are enclosed within catheter sheath 
139 along its length, and exit the catheter through a lumen, which is 
accessible from inside of balloon 140. The wires may also be provided in a 
separate lumen in a two-lumen guide catheter. 
The control module includes an RF power supply that preferably operates at 
650 kilohertz, but can be at any frequency within the range of about 100 
kilohertz to 1 megahertz. The inflation fluid, while selected to have 
resistive losses, has an electrical impedance low enough that it will 
conduct the current supplied by RF power supply at voltages of about 100 
volts or lower, so that there will be no arcing. A full description of a 
suitable RF heated balloon system is described in U.S. application Ser. 
Nos. 07/404,483 filed Sep. 8, 1989 and 263,815 filed Oct. 28, 1988now U.S. 
Pat. No. 4,955,377, the entire contents of both said applications being 
incorporated herein by reference. Furthermore, it will be understood that 
other methods for balloon heating may be employed. 
Referring to FIG. 17d, proximally, the catheter is provided with a 
stationary pressure tight shaft seal 126 that fits in intimate, but 
relatively frictionless contact with a portion of the rotating drive shaft 
162. The seal includes a ball seal 170 (available from Bal-seal 
Engineering Company, Inc., Santa Anna, Calif.), securely held in place by 
a seal holder 172 (stainless steel or elastomer), which abuts the distal 
end of the internal open area of the boot 122 and is held by compression 
of the ferrule assembly 164 (although other means of attachment such as 
injection molding are possible). The seal holder 172 includes a retainer 
sleeve 174 that extends coaxially with respect to the catheter 139. At the 
proximal end, within the ferrule, the drive shaft is held within a gland 
178, preferably formed from hypotubing, which makes relatively 
frictionless contact with the ball seal 170, enabling rotation while 
preventing back flow of inflation fluid into the ferrule. The ball seal, 
as shown, is an annular U-shaped member, including within the U a canted 
coil spring 179 (such that the axis of each coil is tangent to the 
annulus) that presses the legs 175, 177 of the seal radially. The outer 
leg 175 of the seal engages an extension 176 of the seal holder, while the 
inner leg 177 of the seal engages the gland 178. The boot also includes a 
thin (few thousandths of an inch) metal sleeve 171 for additional sealing 
around the catheter. 
The drive shaft 162 is modified in the sealing area 168 by impregnating it 
with a thermoplastic material that fills the gaps in the individual wires 
to prevent flow of inflation fluid through the drive shaft inner lumen at 
typical inflation pressures of 100-120 psi or higher. Alternatively, the 
drive shaft may be sealed by impregnating it with a liquid that is 
hardenable, such as epoxy, and then covering that area with a section of 
cylindrical metal, such as hypotube, in order to form a smooth, fluid 
tight seal capable of holding up to typical balloon pressure. It will also 
be understood that other sealing members may be used, e.g. an 0-ring. 
Preparation of the device is accomplished by the following steps: A Leveen 
inflator is connected to the side arm. The side arm valve is opened and 
air is evacuated by suction. (Generally, the balloon contracts in a folded 
manner which leaves air passages through the interior of the balloon and 
prevents blockage of the passageway 151.) A hypodermic syringe fitted with 
a small gauge needle and filled with a fluid such as water or saline is 
then inserted through the distal tip septum seal. Fluid is introduced 
until surplus exits the side arm, at which point the valve is closed, 
reducing the chances that air will re-enter the catheter. Alternately, the 
fluid may be introduced via the side arm when an air venting needle is 
inserted into the distal septum. 
The catheter is then attached to the driving motor, (not shown), by mating 
the ferrule 124 with a mateable receptacle which connects the ultrasound 
imaging electronics. Imaging can begin as soon as the deflated balloon is 
inserted into a subject lumen. Because the balloon material, saddle and 
sonolucent guide effectively transmit ultrasound energy, continuous 
imaging and monitoring of the subject lumen can be achieved. 
By acoustic imaging, the device may be used to view the lumen and stenoses 
for diagnostic purposes, then the balloon may be positioned accurately in 
any portion of the lumen such as a stenosis, and dilatation of the 
stenotic area may be performed using conventional dilatation technique 
while the progress of treatment is monitored by ultrasonic imaging and 
treatment is modified in response to the observed response of the tissue. 
Finally, after treatment, the balloon may be deflated and the lumen imaged 
to observe the treated site or view other sites. 
The modular construction enables the ultrasound imaging catheter's ability 
to be slidably inserted into a number of different types and styles of 
catheter sheaths. The pressure and fluid tight connector that is mounted 
distally to the location of the side arm connector enables various 
catheters, such as those with balloons of different sizes, to be 
effectively attached at the location of the side arm connector. 
In operation, the acoustic imaging balloon catheter may be used to apply 
pressure (and optionally, heat) to dilate a blood vessel by molding the 
wall or an obstructing material (like plaque). The blood vessel may be a 
coronary artery, or a peripheral artery such as an iliac, femoral, renal, 
carotid, or popliteal artery. The balloon catheter may also be useful for 
dilatations in the biliary tract, esophagus or prostate. 
Referring to Table I, below, preferred apparatus dimensions for various 
treatments are given. 
TABLE I 
__________________________________________________________________________ 
CATHETER 
BALLOON 
DRIVESHAFT 
DIAMETER 
DIAMETER 
BALLOON 
CATHETER 
EXTENSION 
APPLICATION 
DIAMETER (BODY) (INFLATED) 
LENGTH LENGTH LENGTH 
__________________________________________________________________________ 
Coronary .025" 3.0 F 2-3 MM 1.5 CM 140 CM .5 CM 
Arteries 
Valvulo- .054" 6.2 F 14 MM 3 CM 110 CM 1.5 CM 
plasty 
Peripherals 
.040" 6.5 F 7-8 MM 4 CM 95 CM 1.5 CM 
(e.g., 
Iliacs, 
femorals) 
Extremities 
.030" 4.8 F 4-6 MM 3 CM 95 CM 1.5 CM 
Esophogus 
.054" 6.2 F 30 MM 4 CM 95 CM 1.5 CM 
and 
Prostate 
__________________________________________________________________________ 
Referring to FIGS. 18-18e, illustrating dilatation of a blood vessel, a 
percutaneous insertion is made with a needle, and a guide wire is 
introduced into the blood vessel 112. The acoustic imaging balloon 
catheter 110 follows the wire (for example employing the saddle 
arrangement discussed above) and is positioned at an obstruction in the 
artery such as a plaque deposit 114 (FIG. 18) by visualizing the inner 
walls of the artery by acoustic imaging as the catheter is advanced. 
While imaging continues, the balloon 116 is inflated to engage the plaque 
material 114 forming the obstruction (FIG. 18a). As pressure and/or heat 
is applied to the occluding material, the operator views the progress of 
the dilatation to assure that the dilatation does not occur too rapidly, 
which may lead to the formation of cracks or flaps which may in turn lead 
to re-occlusion. 
In the case of a heated balloon catheter, the pressure in the balloon may 
be kept below the normal pressure required under ambient conditions to 
widen the vessel to avoid cracking the plaque. Normal dilation pressure 
means the minimum pressure at which an unheated balloon causes substantial 
dilation of the respective lumen. The low, sub-dilatation pressure used 
initially to engage the plaque material may be, for example, about two 
atmospheres. In the case of angioplasty, normal dilation pressure is of 
the order of 5 to 10 atmospheres (varies with balloon size). The balloon 
self-forms around the irregular surfaces of the obstruction and provides a 
firm contact for efficient and even transfer of heat. As the occlusion 
yields (by virtue of heating and gentle pressure as described below), the 
balloon expands to maintain even contact with the surface. The operator 
monitors the dilatation by acoustic imaging to determine various 
physiological conditions and responses to treatment. 
With the balloon inflated to a low level of pressure and engaging the 
obstruction, the user may initiate the bi-polar heating between the 
electrodes 143, 144 as discussed above, (e.g. by depressing a foot switch 
to start a heating program). Heat is dissipated into the fluid according 
to the formula P=I.sup.2 R where P is the power that is dissipated into 
the fluid, I is the current that is passed through the electrodes, and R 
is the resistance of the fluid. The heat from the fluid is conducted 
across the balloon wall into the surrounding tissue 44. The fluid will 
heat to the temperature set by the user to carry out a temperature 
algorithm. The temperature at the balloon surface ranges from 
45.degree.-90.degree. C. and is typically from 50.degree.to 70.degree. C., 
sometimes preferably, around 60.degree.-65.degree. C. 
While heating, the operator monitors the condition and physiological 
response of the vessel under treatment by acoustic imaging. When the 
obstruction is under certain conditions of heat and pressure, the 
heterogeneous plaque material (usually including fat, fibrogen, calcium) 
softens, resulting in a change in the allowable volume of the balloon at a 
given low pressure (preferably below the pressure needed to crack the 
obstruction). 
In FIG. 18b, for example, the stenoses is observed by acoustic imaging to 
expand slowly as the occluding material elastically (reversibly) expands 
with gentle heating until, upon reaching a yield point at time 
corresponding to the conditions of pressure and temperature at which the 
occlusion yields. Thereafter, the stenoses is observed by acoustic imaging 
to yield at a higher rate as the occluding material yields plastically 
(substantially nonreversibly). 
As shown in FIG. 18c, after observing the yield of the plaque by acoustic 
imaging, the operator determines the course of further treatment, which 
may include maintaining or slight changes in temperature or pressure of 
the balloon, to effect full dilatation of the artery where the continued 
treatment leads to full expansion of the balloon and artery at a time. 
As illustrated in FIG. 18d, after the vessel has been fully dilated, the 
temperature of the balloon is reduced, while the balloon remains inflated. 
Recycling the temperature allows the material of the obstruction, the 
plaque, to be mold-formed by the balloon as it cools and reconstitutes. 
The interior walls of the remodeled lumen are left smooth and with reduced 
chance of re-occlusion. The temperature is reduced while the balloon is 
inflated. 
Finally, as illustrated in FIG. 18e, the balloon is deflated and removed 
from the body lumen. The operator then can observe the dilated vessel by 
acoustic imaging. Referring now to FIG. 19, in another embodiment of the 
acoustic imaging catheter device, the transducer 146 is positioned in the 
distal tip extension of the balloon catheter and distal to the balloon. A 
sonolucent window located distal to the balloon allows imaging to take 
place during the positioning of the balloon and after treatment. In this 
case, ultrasonic energy is not transmitted through the catheter sheath 
190, balloon 191 or saddle 192 as in the previously mentioned embodiments. 
After location and inspection of the area to be treated, the catheter is 
advanced a known amount, e.g. a few centimeters, (monitorable from outside 
the body) and the balloon is inflated. The dilatation is performed, and 
then the balloon is withdrawn, allowing a post dilatation view of the 
region. 
In other embodiments, the transducer may be positioned proximal to the 
balloon. These embodiments may be particularly useful for prostate 
dilatation where the balloon is to be positioned distal to the urinary 
sphincter to avoid dilation of the sphincter. By visualizing the sphincter 
by acoustic imaging with a transducer proximal to the balloon, the 
operator is assured that the balloon is distal to the sphincter. 
Referring now to FIGS. 20-20b, other embodiments of the acoustic imaging 
catheter device allow relative movement of the transducer and balloon so 
that the ultrasound transducer may be positioned in any longitudinal 
position in the balloon, or distal or proximal to the balloon, for an 
assessment, inspection of the body lumen and monitoring of the placement 
of the balloon, the dilatation procedure and then post-treatment 
inspection. In FIG. 20, the drive shaft and transducer 146 may be slid 
axially as indicated by arrows 195 to move the transducer, for example, 
continuously to positions between position I, proximal to the balloon and 
position II, distal to the balloon. A slide assembly 240 is provided 
including a housing 244 having a distal end which receives the catheter 
sheath 139 and drive shaft 145. The drive shaft contacts a pair of 
oppositely arranged, relatively frictionless ball seals 245, 246 press fit 
within the housing against an inner body extension 249 and the distal end 
member 248 of the body which is threaded into the body 244. The ball seals 
engage a gland 250 as discussed with respect to FIG. 17d. The gland is 
attached to a thumb control 252, provided within the body to enable axial 
motion of the drive shaft to position the transducer within the catheter 
corresponding to regions within the balloon and in the distal extension, 
both of which are sonolucent. For example, it may be advantageous, as 
illustrated by the position of the transducer 146 in the series of FIGS. 
18-18e, to position the transducer in the distal extension of the catheter 
during insertion of the catheter to inspect and locate the region to be 
treated by the balloon, then retract the transducer into a region 
corresponding to the balloon to observe dilatation and finally, the 
transducer may be slid forward for post treatment inspection of the lumen 
after balloon deflation. 
The axially translatable transducer device further includes a carbon 
resistor 254 within the slide assembly housing, and contact means 258 
attached to the thumb control and in contact with the resistor. Probe 
wires 256, 257 are connected to the resistor 254 and contact means 258 to 
provide variable resistance between the probe wires as the thumb control 
is slid axially, which is detected at detector 260, to provide monitoring 
of the axial position of the transducer. The thumb control may be hand 
actuated or controlled by automatic translator means 264 which receives 
control signals from a controller 266. In preferred embodiments, the 
output from the detector 260 is provided to an analysis means 268 which 
also receives the acoustic images from the transducer corresponding to 
various axial positions of the transducer within the catheter body to 
provide registry of the images with the axial transducer position on a 
screen 270. In preferred embodiments, the transducer is slid axially, 
along a continuous length or at selected positions of the catheter body, 
for example, from the balloon to the distal tip, and the analysis means 
includes storage means for storing images along the length to reconstruct 
a three-dimensional image of the lumen along the axial length of 
transducer travel. 
FIG. 20b shows an embodiment wherein the catheter includes a bellows member 
280 to enable axial motion of the catheter body with respect to the 
transducer. 
In another embodiment of the acoustic imaging catheter device, the balloon 
is asymmetrical, either or both in shape and expansion capability, and is 
mounted on a catheter shaft that is torquable, and can then be positioned 
using acoustic imaging so that radially selective dilatation is 
accomplished on the desired portion of the lumen wall by torquing the 
catheter. As discussed above, the positioning, rupturing, stretching and 
compression of the lesion and surrounding tissue, and the deflation of the 
balloon can all be monitored with cross-sectional ultrasonic images. 
For example, multiple balloons may be used that are for example, separately 
heated to effect asymmetric heating. The correct orientation of the 
balloons in the lumen can be achieved and confirmed by observation through 
acoustic imaging. Referring to FIGS. 21-22b a balloon catheter 200 
comprises a catheter shaft 202 and at least two balloons 204 and 206. 
Catheter shaft 200 passes through the length of balloon 204. The proximal 
and distal ends of balloon 204 are tacked onto catheter shaft 202 at 
locations adjacent the proximal and distal ends of balloon 204. Catheter 
shaft 202 includes inflation and pressure equalization ports 207, 208 
within balloon 204 through which fluid enters and exits balloon 204, and 
ports 210 and 212 through which fluid enters and exits balloon 206. 
The fully extended diameter of each of the balloons 206 and 208, when 
inflated, typically ranges from 2 millimeters for vascular procedures to 
20 to 35 millimeters for hyperthermia treatment of the prostate, esophagus 
or colon. The combined volume of the balloons ranges from 1/8 cc for the 
smallest balloons to 100 cc for the largest balloons. The wall thickness 
of the balloons 204 and 206 is about 0.001 inch. In some applications, 
e.g. where the catheter 200 is being used in a blood vessel, a guide wire 
214, which can extend past the distal end of the catheter, may be used to 
guide the catheter through the vascular system or other luminal 
structures. The guide wire may also be passed through a saddle as 
discussed above, for example, with respect to FIG. 17a. The exteriors of 
the balloons are coated with a non-stick coating having a low coefficient 
or friction, such as silicone or polysiloxane. The non-heated balloon may 
be covered with a coat of heat-insulating material or silver 
heat-reflective material thereby enhancing the temperature difference 
between the heated balloon and the unheated balloon. 
Balloons 204, 206 are fillable with an electrically conductive fluid such 
as normal saline (0.9 percent NaCl in water), a conductive radiopaque 
fluid, or a mixture of saline solution and a radiopaque fluid. 
In an alternative construction of the embodiment shown in FIGS. 21-21b, 
balloons 204 and 206 may be replaced by a single, multi-segmented balloon. 
Catheter shaft 202 passes through the length of one of the segments. The 
other segment connects with catheter shaft 10 at the locations of lumens 
210 and 212. 
Electrical contacts 218 and 220 which effect heating by RF power 
dissipation, as discussed above are exposed to the fluid inside of one of 
the balloons 204, but are not substantially exposed to the fluid inside of 
the other balloon 206. Within the catheter 200 is positioned a coil-form 
drive shaft 222 (phantom) having at its distal portion an acoustic 
transducer 224. The shaft is rotatable, enabling acoustic imaging of the 
lumen to be treated for positioning of the catheter and balloons, 
monitoring treatment and post-treatment inspection of the lumen. 
In FIG. 21a, the multiple balloon catheter is shown in cross-section along 
lines B--B of FIG. 21. The catheter 202 includes a single lumen 230 which 
rotatably supports the drive shaft 222 as discussed above. Inflation fluid 
for both balloons is passed through the lumen 230 and the inflation ports 
207, 208, 210 and 212 as described above. The location of the heater 
contacts 218, 220 in balloon 206 results in substantial heating of balloon 
204, with only minor conduction of heat and RF power through the catheter 
body to balloon 206. Further details of a multiple balloon catheter 
adaptable to acoustic imaging are discussed in U.S. Pat. No. 5,151,100. 
FIG. 22 and 22a shows sheath 12e, similar to sheath 12, which is 
additionally fitted with an eyelet 90 through a solid portion of the tip 
to allow the free passage of a guide wire 92 which is used to help guide 
the catheter to a region of interest inside a passage of the body. 
FIG. 23 shows sheath 12f having a two lumen construction. The large lumen 
contains the transducer and drive shaft while the small lumen contains a 
wire 94. As shown, wire 94 is a deflecting wire attached near the distal 
end, and is free to slide through its lumen under tension applied to ring 
96 to cause the catheter to bend when pulled taut, thus providing a 
measure of control of the orientation of the distal end of the acoustic 
catheter while negotiating the passages of the body or the like. In 
another embodiment wire 94 may be a preformed stylet, which, when inserted 
through the second lumen, causes deflection of the tip. 
FIG. 24 shows sheath 12g having a small hole 97 at its distal end to allow 
the passage of a fluid under pressure, such as saline or clot dissolving 
enzyme such as urokinase, or radiographic contrast enhancement fluids. By 
this device such fluids can be introduced under precise guidance using the 
ultrasound imaging capability of the catheter. 
FIG. 25 and 25a show sheath 12h placed in a specially designed hollow, 
rigid, sharply pointed metallic trocar 98 similar to a lance, designed to 
be driven into the body and further into the tissue of an organ of 
interest, such as the liver or spleen, to provide ultrasound imaging of an 
area where there is no natural passageway. A side-facing window 99 in the 
distal region of the trocar tube allows the passage of ultrasound energy 
from and to the transducer to enable imaging to take place. Alternatively, 
a portion of the trocar (phantom, FIG. 25a) may be formed of sonolucent 
material, to form an ultrasonic window. The hollow trocar tube serves 
further to prevent crushing or deformation of the ultrasound catheter 
under the considerable pressure required to drive the device into solid 
body tissue. After ultrasound inspection the imaging catheter may be 
withdrawn from this device and a biopsy device may then be inserted in its 
place with the advantage that the region from which the biopsy is to be 
taken has been very accurately located by acoustic imaging. 
The acoustic imaging-trocar apparatus is useful, for example for diagnosis 
of tumors in the liver. Typically liver cancer is first evidenced by a 
number of very small tumors that are diffuse and randomly located making 
them difficult to visualize by external ultrasound apparatus. By employing 
the acoustic imaging-trocar apparatus of the present invention early 
detection of cancerous tumors may be accomplished by driving the 
ultrasound catheter inside the trocar into the liver where small tumors 
are suspected or likely to be. By driving the catheter into the tissue, 
although there is no natural passageway, the operator can search for 
tumors in the field of view. When a tumor is found the operator can remove 
the ultrasound imaging catheter and place within the trocar a biopsy 
sampling instrument such as forceps 284 to collect a small portion of the 
tumor (FIG. 25b). The forceps jaws 283, 285 are moveable from proximal 
portions as indicated by arrows 287 to open and close the instrument to 
grasp a sample. Similar procedures may be carried out in the breast, in 
searching for small tumors. In general the benign tumors are more or less 
encapsulated whereas cancerous tumors have a diffuse edge therefore 
enabling a preliminary analysis of the tumor by acoustic imaging. In 
another embodiment, shown in FIG. 25c, the trocar may include at its 
distal end, in the vicinity of the transducer a radioactive pellet 286, 
for radiation treatment of tumors found by ultrasonic imaging. 
FIG. 26 shows flexible, disposable sheath 12i made of integral, thin-walled 
extruded plastic which is more or less sonolucent. This construction 
avoids the necessity of having a separate dome or window attached to the 
distal end. The distal end is post formed (thinned, e.g. by drawing and 
blowing) after extrusion to provide the correct wall thickness dimension 
for best sonic transmission and mechanical strength and may be sealed 
fluid tight at the tip. 
FIG. 27 shows sheath 12j which is similar to sheath 12i of FIG. 26, and 
additionally has an integral floppy tip made by continuing the drawing 
process to form a small diameter solid but flexible extension of the 
sheath beyond the sonolucent area; it can achieve certain of the 
advantages of catheter 12a of FIG. 13 but without the additional cost of 
adding a separate metal floppy guide wire. 
FIG. 28 shows sheath 12k which is formed to have an inner end bearing 
surface 101 at the distal tip for serving as an axial and radial bearing 
for the rotating ultrasound transducer. This bearing is e.g. a small 
spherical or conical formation. By applying an axial, distal thrust on the 
shaft, and axial proximal tension on the catheter sheath, this bearing 
action creates tension on the tapered area of the dome, thus maintaining 
its shape by stretching, and allowing an even thinner material to be used, 
to reduce loss of acoustic energy in the substance of the window. 
FIG. 29 and 29a show sheath 121 which is fitted with a keyed rotating shaft 
that accepts the end of a similarly keyed ultrasound transducer, and acts 
as a power takeoff for driving a rotatable instrument such as the 
atherectomy cutter 105, shown. 
FIGS. 30-30c show a sheath constructed along the lines of sheath 12a of 
FIG. 13, being used in guiding and penetrating through the moving opening 
of a human heart valve. It shows how the floppy guiding wire acts as a 
stabilizer and a centering device allowing the ultrasound device to be 
moved forward and withdrawn repeatedly and consistently, as is desirable 
for proper imaging of the valve before and after valvuloplasty. 
FIG. 31 shows an integrally-formed catheter sheath having an acoustic 
window 24i originally of the same extruded material as the body of the 
catheter, the material of the window being modified to enhance its 
acoustic window properties. In this embodiment the main body 12.sub.mb of 
the sheath has wall thickness t of 0.4 mm and outer diameter D of 2 mm. 
The integral window 24.sub.i has outer diameter D corresponding to that of 
the main body of the catheter and a modified wall thickness t.sub.1 of 0.2 
mm. Any of these catheters may be additionally fitted with radiopaque 
markers either at the tip or the middle or both, designed to be visible 
when seen under the fluoroscope while intraluminal ultrasound imaging 
takes place. The markers are made of a metallic material that blocks X-ray 
radiation or a metal filled adhesive or epoxy is applied to the surface, 
in a groove, or at the end of the device. Additionally the metal-filled 
epoxy may be used to seal the end of the device as well as provide 
radiopacity. 
Other embodiments are within the following claims.