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Description  |
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FIELD OF THE INVENTION
This invention generally relates to diagnostic and therapeutic methods and
apparatus using ultrasonic energy, and more particularly to such methods
and apparatus particularly adapted for use with an endoscope to provide
blood flow detection.
BACKGROUND OF THE INVENTION
Flexible endoscopes including optical fibers are used for a variety of
endoscopic procedures such as endoscopic papillotomy and the evaluation of
esophageal varices, arteriovenous malformations, ulcer vessels, ischemic
bowel disease, and polyps.
Endoscopic papillotomy is a nonoperative technique which enables relief of
common bile duct obstruction due to retained gallstones. In this
technique, a flexible endoscope is inserted into the duodenum and advanced
until the entrance to the common bile duct and the pancreatic duct (i.e.,
the papilla of Vater) can be visualized. A papillotome catheter is then
passed through the biopsy channel of the endoscope until the catheter tip
exits from the endoscope tip, and the endoscope tip is remotely
manipulated and the papillotome catheter is concurrently advanced so as to
insert the papillotome catheter into the common bile duct. Along its side
adjacent its tip, the papillotome catheter carries an elongated wire that
can be remotely bowed so as to bear upon the roof of the papilla. By
passing an electrosurgical current through the wire when the papillotome
catheter has been appropriately positioned and bowed, the roof of the
papilla of Vater may be cut so as to enlarge the papilla orifice. After
withdrawal of the papillotome catheter, the retained gallstones in the
common bile duct may naturally migrate into the duodenum or may be removed
by a grasping device passed through the biopsy channel of the endoscope.
In certain patients, the retroduodenal artery is quite close to the papilla
and may be cut by the papillotome catheter, thereby leading to morbidity
and mortality complications. To reduce the risk of endoscopic papillotomy,
it is highly desirable to determine the location of the retroduodenal
artery relative to the papilla of Vater by detecting the presence and
characteristics of blood flow in the retroduodenal artery.
Esophageal varices are dilated veins on the inner surface of the esophagus,
most typically resulting from cirrhosis of the liver, and quite often
bleed. Although pharmaceutical and surgical methods typically are used to
treat esophageal varices, an endoscopic technique also may be used in
which a flexible endoscope is inserted into the esophagus and advanced
until a varix is visualized. A catheter having a hollow needle at its tip
is then passed through the biopsy channel of the endoscope so that the
needle exits from the endoscope tip, and the endoscope tip is remotely
manipulated and the catheter is concurrently advanced until the needle is
inserted into the varix. A sclerosing agent is then injected through the
catheter and the needle into the varix in order to thrombose or clot the
varix.
Occasionally, a heavy esophageal mucosal fold may mimic the appearance of a
varix. It is therefore highly desirable to determine if the visualized
target is a varix by the detection of venous flow before needle insertion
and sclerosing agent injection. It is also highly desirable to determine
the effect of the injected sclerosing agent in the event the target is a
varix by the detection of a reduction in and eventual absence of venous
flow.
Another type of lesion which causes problematic gastrointestinal bleeding
is that of an arteriovenous malformation which can be visualized through
the use of a flexible endoscope as a small red dot on the mucosa of the
gut. Unfortunately, it is often very difficult to tell if such a red spot
is an adherent clot, a petechiae or an arteriovenous malformation. It is
therefore highly desirable to positively determine such a red spot as an
asteriovenous malformation by the detection of arterial blood flow.
In a similar manner, the evaluation of ulcerations in the stomach or
duodenum and of techniques being used to thrombose such ulcerations, the
diagnosis of ischemic bowel disease, and the evaluation of the size of the
blood vessels in the stalks of gastrointestinal polyps by use of a
flexible endoscope would be facilitated by detecting the presence and
characteristics of proximate blood flow.
Rigid endoscopes are used for a variety of endoscopic procedures such as
peritoneoscopy, arthroscopy, proctoscopy, thoracoscopy and cystoscopy. As
with flexible endoscopic procedures, rigid endoscopic procedures would
benefit immensely from the detection of the presence and characteristics
of proximate blood flow. For example, in the examination of an organ such
as the liver in peritoneoscopy, a mass may be encountered. If the mass is
an arteriovenous malformation, biopsy of the mass may result in severe
life-threatening hemorrhage which could be prevented by the prior
determination of the mass as an arteriovenous malformation through the
detection of arterial blood flow therein.
In addition to the endoscopic procedures discussed, many surgical
procedures would benefit from the detection of proximate blood flow. As
examples, the detection of arterial blood flow proximate the site of an
abdominal aneurysm repair or a coronary artery bypass would allow
assessment of the success of the surgical procedure. Just as it is often
difficult for the endoscopist to determine if a biological structure is
vascular, the same problem may occur for the surgeon, and it may be very
important to determine if a biological structure about to be biopsied or
removed is highly vascular.
Besides detecting blood flow during endoscopic and surgical procedures, the
long-term monitoring of blood flow and differentiation of arterial from
venous flow in biological structures is highly desirable. For example,
long-term monitoring of blood flow in an artery would permit simultaneous
monitoring of heart rate and of an indication of impending shock or a
change in cardiac output.
In the prior art, detection of blood flow in biological structures is
accomplished by evaluation of a Doppler signal obtained from an ultrasonic
transducer that ensonifies the biological structure. As of the present, no
practical methods or apparatus providing a Doppler signal have been
devised which can be successfully used with the endoscopic, surgical and
monitoring diagnostic and therapeutic methods discussed above. In order to
meet the requirements of such methods, the ultrasonic apparatus must be
small in diameter and flexible so as to be capable of being passed through
the biopsy channel of an endoscope or otherwise inserted into the body,
must be nontoxic and must be resistant to bodily fluids when left within
the body, must be capable of detecting blood flow in the biological
structure of interest and of distinguishing the detected blood flow from
that in adjacent biological structures, and must be capable of detecting
the characteristics of blood flow so as to distinguish between arterial
and venous flow.
SUMMARY OF THE INVENTION
In its broadest sense, the invention resides in a method for identifying
and monitoring an intracorporeal biological structure. The method
comprises the steps of: inserting an endoscope into the body; visualizing,
through the endoscope, the location of the biological structure; passing a
catheter including an ultrasonic probe through a biopsy channel of the
endoscope and into proximity to the biological structure; and, monitoring
a Doppler signal obtained from the ultrasonic probe for that Doppler
signal characteristic of blood flow in the biological structure.
Exemplary applications in which such a method may be used are endoscopic
papillotomy and the evaluation and treatment of esophageal varices.
In endoscopic papillotomy, the location of the retroduodenal artery
relative to the papilla of Vater may be determined by inserting a
flexible, side-viewing endoscope into the duodenum. After visualizing the
papilla through the endoscope, a catheter including an ultrasonic probe
having a transverse, sectorial, range-limited field is passed through a
biopsy channel of the endoscope, through the papilla, and into the common
bile duct so that the ultrasonic field is directed toward the
retroduodenal artery. The catheter is advanced and a Doppler signal
obtained from the probe is monitored until the Doppler signal is
characteristic of arterial blood flow. Then, the amount by which the
catheter has been advanced past the papilla is visualized through the
endoscope.
Alternatively, the probe of the catheter may have an omni-directional
field. Such a catheter may be brought into contact with the duodenum and
advanced along the duodenum until the Dopper signal obtained from the
probe is characteristic of arterial blood flow. The location of the probe
relative to the papilla is then visualized through the endoscope.
In the evaluation of esophageal varices, a flexible, end-viewing endoscope
is inserted into the esophagus. After visualizing a protrusion in the
esophagus through the endoscope, a catheter including an ultrasonic probe
having a range-limited ultrasonic field is passed through a biopsy channel
of the endoscope and into the esophagus until the probe contacts the
protrusion. A Doppler signal obtained from the ultrasonic probe is then
monitored for that Doppler signal characteristic of venous blood flow.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention can best be understood by reference to the following portion
of the specification, taken in conjunction with the accompanying drawings
in which:
FIG. 1 is a pictorial view of a papillotome catheter including an
ultrasonic probe;
FIG. 2 is a pictorial view illustrating the use of the papillotome catheter
of FIG. 1 in endoscopic papillotomy;
FIG. 3 is a longitudinal cross-sectional view of the papillotome catheter
of FIG. 1;
FIG. 4 is a pictorial view of another form of catheter including an
ultrasonic probe that can be used in endoscopic papillotomy;
FIGS. 5 and 6 are schematic views illustrating the use of the catheter of
FIG. 4 during endoscopic papillotomy;
FIGS. 7A, 7B and 7C are longitudinal cross-sectional views of a catheter
including one form of a side-viewing ultrasonic probe;
FIGS. 8A and 8B are respective longitudinal and transverse cross-sectional
views of a catheter including another form of a side-viewing ultrasonic
probe;
FIG. 9 is a pictorial view illustrating the use of a catheter including an
ultrasonic probe in the evaluation of esophageal varices;
FIGS. 10A and 10B are longitudinal cross-sectional views of a catheter
including one form of an end-viewing ultrasonic probe;
FIG. 11 is a longitudinal cross-sectional view of a catheter including
another form of an end-viewing ultrasonic probe;
FIG. 12 is a pictorial view illustrating the sclerosing of an esophageal
varix by the use of a sclerosing catheter including an ultrasonic probe
and a sclerosing needle;
FIG. 13 is a longitudinal cross-sectional view of a sclerosing catheter
including a side-viewing ultrasonic probe;
FIG. 14 is a longitudinal cross-sectional view of a sclerosing catheter
including one form of an end-viewing ultrasonic probe;
FIG. 15 is a longitudinal cross-sectional view of a sclerosing catheter
including another form of an end-viewing ultrasonic probe;
FIG. 16 is a block diagram of a Doppler circuit to be used with the
catheters previously discussed;
FIG. 17 is an electrical schematic of an isolation circuit for coupling the
ultrasonic probe of such a catheter to the Doppler circuit;
FIG. 18 is a pictorial view of a transformer included in the isolation
circuit; and,
FIGS. 19 and 20 are electrical schematics of additional isolation circuits.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention initially will be described with reference to its use with
endoscopic papillotomy and then with respect to its use in the evaluation
and treatment of esophageal varices. The invention is not limited to these
two techniques, however, and is broadly applicable to intracorporeal blood
flow detection in conjunction with many diagnostic and therapeutic methods
such as those previously discussed.
Referring now to FIG. 1, a papillotome catheter similar to those previously
known and used but modified for the detection of blood flow includes as
its major components an elongated, cylindrical tube 10 of flexible
material, an elongated wire 12 carried by tube 10, and an ultrasonic probe
14 disposed at the tip of tube 10. As will be discussed in conjunction
with FIG. 3, one end of wire 12 terminates within tube 10 proximate
ultrasonic probe 14. From that end, wire 12 extends through an opening 16
in tube 10, along the exterior of tube 10, then back through an opening 18
in tube 10 and thence within and through the remaining length of tube 10
to and beyond its distal end (not illustrated). Normally, the portion of
the catheter illustrated in FIG. 1 is yieldably biased to a substantially
linear configuration wherein wire 12 lies on the exterior of tube 10. When
tension is applied to the distal end of wire 12, however, the catheter is
bowed to the configuration illustrated in FIG. 1 so that wire 12 bears
against body tissue which may then be cut by the passage of an
electrosurgical current through wire 12.
Ultrasonic probe 14 includes an ultrasonic transducer that is capable of
ultrasonic energy transmission and reception in directions transverse
(i.e., at an angle) and preferably normal to the longitudinal axis of tube
10. The ultrasonic transducer is connected to a Doppler circuit described
hereinafter with reference to FIG. 16 by means of leads (not illustrated)
disposed within tube 10. As described in detail hereinafter, the
ultrasonic transducer within ultrasonic probe 14 is provided with a high
frequency electrical signal (the transmitted signal) which is converted by
the ultrasonic transducer into ultrasonic energy. Returned ultrasonic
energy is converted by the ultrasonic transducer into a corresponding
electrical signal (the received signal) which is compared in the Doppler
circuit with the transmitted signal to develop a Doppler signal related to
the frequency shift between the transmitted signal and the received signal
occasioned by the movement of objects including blood through the region
ensonified by the ultrasonic transducer.
Referring now to FIG. 2, a simplified pictorial view of the anatomy in the
region of interest in endoscopic papillotomy includes the descending
duodenum 20 into which protrudes the papilla of Vater 22. The papilla
includes an orifice communicating with both the common bile duct 24 and
the pancreatic duct 26. Typically, common bile duct 24 and pancreatic duct
26 are surrounded by pancreatic tissue 28 which extends to the duodenum
20. A major blood supply to common bile duct 24 is provided by the
retroduodenal artery 30, a portion of which passes between common bile
duct 24 and duodenum 20.
The technique of endoscopic papillotomy is used in the treatment of
gallstones that are retained in common bile duct 24. In this technique, a
flexible, side-viewing endoscope 32 having optical fibers 34 and 36 and a
biopsy channel 38 terminating in its side adjacent its tip is inserted
into duodenum 20 and advanced until papilla 22 can be visualized through
an optical system of the endoscope including optical fibers 34 and 36. The
papillotome catheter of FIG. 1 is then inserted into and advanced along
biopsy channel 38 until the catheter tip exits from the biopsy channel. By
remote manipulation of the endoscope and catheter tips and by concurrent
advancement of the catheter, the catheter tip is passed through the
orifice of papilla 22 and into common bile duct 24 so that wire 12 faces
the roof or upper portion of the papilla. Remote tension is then applied
to wire 12 so that the papillotome catheter assumes its bowed
configuration to press wire 12 against the upper portion of the papilla,
and a radio frequency electrosurgical current is then passed through a
circuit including wire 12 and a ground plate (not illustrated) attached to
the patient so as to cut the upper portion of the papilla as illustrated.
Upon withdrawal of the papillotome catheter, the retained gallstones may
be removed by a grasping device passed through biopsy channel 38 and the
now-enlarged orifice of the papilla into common bile duct 24, or, may be
allowed to naturally migrate into duodenum 20 through the now-enlarged
orifice of the papilla.
Generally, the portion of retroduodenal artery 30 illustrated in FIG. 2 is
more than 3 cm from the orifice of papilla 22. In a significant number of
patients, however, this distance may be less than 3 cm and may be as small
as 1.0 cm. Therefore, there is the distinct possibility that cutting of
the papilla in endoscopic papillotomy may also cut the retroduodenal
artery, leading to hemorrhage and other complications. It is therefore
highly desirable to determine the location of the retroduodenal artery
relative to the papilla orifice. In doing so, the papillotome catheter is
advanced in its normal, unbowed configuration along common bile duct 24
and the Doppler signal obtained from the ultrasonic transducer in
ultrasonic probe 14 is monitored until that Doppler signal characteristic
of arterial blood flow is obtained. The amount by which the papillotome
catheter has been inserted into common bile duct 24 may then be visualized
by use of endoscope 32, allowing an estimate to be made of the location of
retroduodenal artery 30 relative to the orifice of papilla 22. If the
retroduodenal artery is found to be too close to the papilla orifice, a
decision may be made to abort endoscopic papillotomy and to treat the
gallstones with pharmaceutical or surgical methods.
In order to provide successful detection of intracorporeal blood flow by
means of an apparatus including a catheter having an ultrasonic probe, a
number of requirements must be met.
First, the ultrasonic probe must be small enough so that it can be passed
through the biopsy channel of an endoscope while yet allowing the biopsy
channel to be alternately or simultaneously shared for other purposes. In
this regard, the papillotome catheters used in the past for endoscopic
papillotomy have an outer diameter of 1.8 mm, so the diameter of the
catheter tube and of the ultrasonic probe preferably are equal to or less
than that diameter.
Second, the apparatus must be capable of detecting blood flow in the region
of interest, a task which is made quite difficult by the limited control
available for positioning of the ultrasonic probe in endoscopic
applications.
Third, the apparatus must be able to detect blood flow within 1 mm of the
probe. In the region of interest in endoscopic papillotomy illustrated in
FIG. 2, the maximum thickness of pancreatic tissue 28 between common bile
duct 24 and duodenum 20 is approximately 1.5 to 2.0 cm, whereas the
minimum thickness of such tissue (i.e., that adjacent papilla 22) is
approximately 3 mm. In some cases, the retroduodenal artery 30 may be
located about 1 mm from the adjacent surface of common bile duct 24.
Fourth, the apparatus must be safe to use. Since the probe is to be placed
in the body in close proximity to the heart and other vital organs,
electrical safety is especially important. In the endoscopic papillotomy
application, the presence of the probe within the common bile duct
requires that the probe be nontoxic and that the probe be resistant to
bodily fluids within the duct.
Fifth, it is necessary in many applications, including those of endoscopic
papillotomy and in the valuation and treatment of esophageal varices, to
limit the range of the apparatus to about 4 to 5 mm in order that blood
flow occurring in the body outside of the particular region of interest
does not mask blood flow within the region of interest.
Sixth, the apparatus must be capable not only of detecting blood flow, but
also of characterizing the detected blood flow as either arterial flow or
venous flow and of distinguishing such flow from other components of
motion in the region of interest, such as vessel wall motion.
Specific attention to these requirements has been given in the design of
not only the catheter but also the Doppler circuit with which the catheter
is used.
Now referring to FIG. 3, ultrasonic probe 14 includes a substantially
cylindrical member 40 of a metallic (e.g., brass) material or of a plastic
(e.g., acrylic) material whose exterior surface is covered with a layer of
electrically conductive material, such as a conductive epoxy resin or a
metallic plating. Around its periphery, member 40 is provided with an
annular groove 42 and with spaced-apart, annular ridges 44. The outer
diameter of that portion of member 40 bearing ridges 44 is substantially
equal to the inner diameter of tube 10 so that member 40 may be inserted
into the end of tube 10 and retained therein by the engagement of ridges
44 with the inner wall of the tube. Tube 10 preferably is composed of
polyethylene or Teflon.TM. having an outer diameter of approximately 1.8
mm and a length in the range of 120 cm to 200 cm. An ultrasonic transducer
46 comprising an annular, cylindrical ring of piezoelectric material
having metallic, conducting layers 50, 52 formed on its inner and outer
cylindrical surfaces, respectively, is disposed on member 40 and overlies
groove 42. The outer diameter of transducer 46 is preferably equal to that
of tube 10. Inner conductive layer 50 is electrically connected to member
40 by soldering or by the use of an electrically conductive epoxy resin,
and outer conductive layer 52 is electrically connected to the center
conductor 54 of a microcoaxial cable 56 passing through a central,
longitudinal bore 58 within member 40. The electrical connection of inner
conductive layer 50 to member 40 also serves to secure transducer 46 to
member 40. An outer conductive sheath 60 of cable 56 is terminated within
bore 58 and is electrically connected to member 40. In place of cable 56,
a twisted pair of wires may also be used. The catheter is completed by a
coating 62 of a nonconductive epoxy resin that forms a smoothly rounded
tip of the catheter covering and insulating center conductor 54 and that
forms a thin layer extending from that tip over transducer 46 and onto an
adjacent portion of tube 10.
A thin, flat and elongated spring 64 is disposed within tube 10 adjacent
probe 14. Wire 12 passes through an opening 66 in spring 64, through
opening 18 in tube 10, along the exterior of tube 10, back through opening
16 in tube 10, and through an opening 68 in spring 64. A ferrule 70 is
crimped or welded to the end of wire 12 and prevents wire 12 from being
pulled out through openings 68 and 16 when tension is applied to wire 12.
Spring 64 tends to maintain the catheter in a linear configuration as
illustrated in FIG. 3. When tension is applied to wire 12 so that the
catheter assumes its bowed configuration as illustrated in FIG. 1, spring
64 further serves to prevent the flexible material of tube 10 from being
cut or otherwise deformed by wire 12 and ferrule 70. In place of spring
64, an elongated coil spring similar to that found in prior papillotome
catheters may be used provided that sufficient space remains within tube
10 for wire 12 and cable 56.
Wire 12 and cable 56 extend from the catheter tip illustrated in FIG. 3
along the length of the catheter and exit from the distal end thereof. The
exiting end of wire 12 is connected to an appropriate source of an
electrosurgical current (not illustrated), and the exiting center
conductor 54 and outer conductive sheath 60 of cable 56 are connected
through an isolation circuit described hereinafter in conjunction with
FIGS. 17-20 to the Doppler circuit described hereinafter in conjunction
with FIG. 16.
The catheter illustrated in FIG. 3 is assembled in the following manner.
Openings 16 and 18 are formed near the end of tube 10. One end of wire 12
is then inserted through opening 68 in spring 64 and the resultant
assembly is inserted into tube 10. The end of wire 12 is then advanced
until it exits from opening 16, back through opening 18 and opening 66,
and then to the distal end of tube 10 (not illustrated). At this point,
ferrule 70 is applied to the other end of wire 12 to complete the assembly
of wire 12 and spring 64 within tube 10.
After member 40 has been fabricated by a technique appropriate to the
material thereof, ultrasonic transducer 46 is fitted thereon and inner
conductive layer 50 thereof is electrically connected to member 40. Cable
56 is passed through the entire length of tube 10, the end of cable 56 is
appropriately stripped, and the stripped portion is inserted through bore
58 in member 40. Inner conductor 54 is then electrically connected to
outer conductive layer 52 of ultrasonic transducer 46 and outer conductive
sheath 60 is electrically connected to member 40 within bore 58. Member 40
is then inserted into the end of tube 10. Either prior to or subsequent to
this step, the periphery of tube 10 adjacent member 40 is treated with a
solution which permits chemical bonding to the material of tube 10. For
example, a solution such as Tetra Etch.TM., specially designed for
pre-treating Teflon for the purpose of chemical bonding, may be used. The
catheter tip is then dipped into liquid, uncured epoxy resin so that a
portion of tube 10 is contained within the resin, removed, and heat
treated until the resin has cured.
The small size requirement of ultrasonic probe 14 is met by member 40 that
provides a solid, stable and accurate base to which ultrasonic transducer
46 may be secured and electrically connected and that permits the probe to
be inserted into and retained at the end of a conventional catheter tube
such as tube 10. By the use of a pulsed Doppler approach as discussed
hereinafter, a single transducer can be used for both the transmission and
reception of ultrasonic energy, thereby making it easier to meet the small
size requirement in fabrication of the probe.
Because it may be difficult to control the position of the probe in
endoscopic applications, a highly directional transducer is generally
undesirable in such applications. This problem is addressed by the use of
the annular, cylindrical form of ultrasonic transducer 46 that provides an
unfocused ultrasonic field transverse and substantially normal to the
longitudinal axis of tube 10. Although the ultrasonic field may be
omnidirectional, it is preferred in the papillotome catheter that the
field traverse a partial, yet fairly wide sector. Such a sectorial field
may be achieved by longitudinally cutting outer conductive layer 52 at two
spaced-apart locations corresponding to the desired sector after
ultrasonic transducer has been mounted on member 40, and by electrically
connecting center conductor 54 only to the portion of outer conductive
layer 52 between these two cuts. Further, the cuts are made so that the
desired sectorial field extends from the "inner" curve of the papillotome
catheter, that is, the side of tube 10 along which wire 12 extends. The
ultrasonic field may then be easily directed toward the retroduodenal
artery by visualizing the position of wire 12.
The requirement of close proximity blood flow detection is addressed by the
provision of groove 42 which provides an air backing for ultrasonic
transducer 46. Since very little ultrasonic energy can be transmitted
through air from the transducer because of the large difference in
acoustic impedance between air and the piezoelectric material of the
transducer, almost all of the ultrasonic energy produced by the transducer
is radiated from the outer surface thereof covered with outer conductive
layer 52. As a result, probe sensitivity is increased while avoiding
entrapment of ultrasonic energy in member 40. If not compensated for,
entrapment would produce multiple reverberations of transmitted ultrasonic
energy in the probe which would take considerable time to damp, which
damping time would block the Doppler circuit from analyzing received
ultrasonic energy from blood flow in close proximity to the transducer.
The use of air as a backing material is preferred because the small size
of the probe makes it difficult to use another absorptive material as the
backing material.
Close proximity detection is also enhanced by the annular, cylindrical form
of ultrasonic transducer 46, which permits, in close proximity to the
probe, angles of encounter other than 90.degree. between the direction of
blood flow and the direction of propagation of some of the transmitted
ultrasonic energy. As is well known, no Doppler shift would be present if
all angles of encounter between the blood flow and the transmitted
ultrasonic field were 90.degree.. The use of a highly directional
transducer in the probe would make it difficult to detect blood flow if
the probe were placed immediately adjacent a blood vessel. Taking the
endoscopic papillotomy application as an example and referring back to
FIG. 2, let it be assumed that retroduodenal artery 30 is within 1 mm of
common bile duct 24. If probe 14 were to have a highly directional field,
which can be visualized as a line in the plane of FIG. 2, it will be seen
that blood flow in the retroduodenal artery in that field will always be
perpendicular thereto. In contrast, the use of the unfocused radial field
produced by transducer 46, which field can be visualized as a plane
transverse to the plane of FIG. 2, will result in some of the blood in the
retroduodenal artery encountering transmitted ultrasonic energy at angles
other than 90.degree.. Yet another advantage of a radial field is that
such a field has fewer near-field maximum and minimum intensity points
than a highly directional field, thereby further enhancing close proximity
detection of blood flow.
Concerning safety, this requirement is addressed by the use of epoxy
coating 62 that is preferably composed of a biocompatible, nontoxic and
nonconductive epoxy resin. Because coating 62 covers the entirety of
member 40, transducer 46, and inner conductor 54, it protects these
elements from any fluids encountered within the body, maintains electrical
isolation between the conductive elements of the probe and body tissue,
and prevents the potentially toxic materials of the probe from coming into
contact with body tissue. Since a portion of coating 62 extends over a
portion of tube 10, coating 62 also assists in securing the probe to the
tube.
The requirement of close proximity detection, as well as the requirements
of range limiting, separation of venous and arterial flow and wall motion,
and safety, are also addressed by the Doppler circuit of FIG. 16 as
discussed hereinafter.
Referring now to FIG. 4, another form of a catheter usable in endoscopic
papillotomy and other endoscopic and non-endoscopic applications includes
an elongated, cylindrical tube 100 of flexible material having an
ultrasonic probe 102 disposed at its tip. Along its exterior, tube 100 is
provided with a longitudinally extending marking 104 that is preferably
situated on an "inside" curve of the catheter formed by heat treating tube
100 to the curved configuration illustrated in FIG. 4. Preferably, probe
102 includes an annular, cylindrical transducer that has either an
omnidirectional field transverse to the longitudinal axis of tube 100 or a
transverse sectorial field aligned with marking 104 in a manner similar to
the alignment of the sectorial field of transducer 46 with wire 12 in the
papillotome catheter of FIG. 3. At regularly spaced intervals along its
length, tube 100 is provided with transverse and circumferentially
extending markings 106, 108 and 110, each of which indicates a
predetermined incremental distance (such as 1 cm) from probe 102.
The catheter of FIG. 4 may be used in two different ways in endoscopic
papillotomy, as illustrated in FIGS. 5 and 6.
In FIG. 5, the catheter of FIG. 4 preferably includes a probe 102 having a
transverse omnidirectional field. The catheter is advanced through biopsy
channel 38 of endoscope 32 until the catheter tip exits therefrom. The
endoscope and catheter tips are then remotely manipulated, and the
catheter concurrently advanced, so that the catheter slides along the side
of duodenum 20 proximate retroduodenal artery 30. The process of catheter
advancement continues until a Doppler signal characteristic of arterial
blood flow is detected to indicate that probe 102 is proximate the
retroduodenal artery. At this point, the transverse markings on tube 100
are visualized together with the papilla 22 in order to form an estimate
of the location of the retroduodenal artery relative to the papilla.
In FIG. 6, the catheter preferably includes a probe 102 having a transverse
sectorial field. The catheter tip is inserted into common bile duct 24,
with the catheter being rotated so that the longitudinal marking on tube
100 faces the side of the common bile duct proximate retroduodenal artery
30, wherein the sectorial field is directed towards the retroduodenal
artery. When a Doppler signal characteristic of arterial blood flow is
detected, the location of the retroduodenal artery relative to the papilla
may again be estimated by visualization of the transverse markings on tube
100 and of papilla 22.
In both procedures, the catheter of FIG. 4 is withdrawn from the endoscope
after the relative location of retroduodenal artery 30 has been estimated.
If the estimate indicates that there is no significant probability of
cutting the retroduodenal artery during endoscopic papillotomy, a standard
papillotome catheter is then advanced through the biopsy channel and used
in a manner similar to that previously described for the papillotome
catheter of FIG. 1.
FIGS. 7A, 7B and 7C illustrate one form of probe 102 that is substantially
similar to the form of probe 14 illustrated in FIG. 3. As such, probe 102
includes a substantially cylindrical member 112 of a metallic material or
of a plastic material covered with a conductive layer. An ultrasonic
transducer 114 is disposed on member 112 and overlies a peripheral annular
groove 116 therein. The ultrasonic transducer has an inner conductive
layer 118 electrically connected to member 112 and an outer conductive
layer 120 to which is electrically connected a center conductor 122 of a
microcoaxial cable 124 that passes through a central bore 126 of member
112 and whose outer conductive sheath 128 is electrically connected to
member 112 within that bore. The outer diameter of member 112 is
substantially equal to the inner diameter of tube 100, and member 112 is
provided with spaced-apart, annular ridges 130 on its periphery which
assist in securing probe 102 to tube 100 when member 112 is inserted into
the end thereof. The catheter is completed by a coating 132 of a
nonconductive epoxy resin that forms a thin layer over ultrasonic
transducer 114 and the adjacent portion of tube 100 and that terminates in
a smoothly rounded tip covering and insulating center conductor 122.
The ultrasonic field of the probe may be omnidirectional, as illustrated in
FIG. 7A, or may be sectorial, as illustrated in FIG. 7B in which outer
conductive layer 120 is provided with spaced-apart, longitudinal cuts 134,
136 that divide outer conductive layer into portions 120A, 120B and in
which center conductor 112 is electrically connected only to portion 120A.
A catheter particularly adapted for non-endoscopic applications and for
those endoscopic applications in which a directional ultrasonic field can
be used is illustrated in FIGS. 8A and 8B. The catheter includes an
elongated, cylindrical tube 140 of flexible material and an ultrasonic
probe 142 disposed at the tip of tube 140. Probe 142 includes a
substantially cylindrical member 144 of a metallic material or of a
plastic material covered with a conductive layer that has a smoothly
rounded tip. On one side, member 144 has a flat surface 146. A rectangular
recess containing a flat, ultrasonic transducer 148 extends into member
144 from surface 146, and a further recess 150 underlies ultrasonic
transducer 148. An inner conductive layer 152 of transducer 148 is
electrically connected to member 144, and an outer conductive layer 154 of
transducer 148 is electrically connected to a center conductor 156 of a
microcoaxial cable 158 disposed within an off-axis bore 160 in member 144
that terminates adjacent surface 146. Outer conductive sheath 162 of cable
158 is electrically connected to member 144. At its end away from its
smoothly rounded tip, member 144 has an outer diameter that is
substantially equal to the inner diameter of tube 140. Spaced-apart,
annular ridges 164 on the periphery of member 144 assist in retaining
probe 142 on the tip of tube 140 when member 144 is inserted therein. The
catheter is completed by a coating 166 of a nonconductive epoxy resin that
forms a thin layer over all exterior surfaces of member 144, transducer
148, center conductor 156, and the adjacent portion of tube 140.
As previously discussed, another situation in which it is desirable to
detect blood flow is in the evaluation and treatment of esophageal
varices. Referring now to FIG. 9, a flexible, end-viewing endoscope 170
has been inserted into esophagus 172. Endoscope 170 has optical fibers 174
and 176 terminating in an end face thereof that permit the interior of
esophagus 172 to be visualized, and a biopsy channel 178 also terminating
in the end face through which a catheter or other device may be passed. On
the inner surface of esophagus 172, a number of protrusions 180, 182 and
184 are present. In order to determine whether any of the protrusions is a
varix, the protrusion is first visualized by remote manipulation of the
endoscope tip. Then, a catheter including an elongated tube 186 of
flexible material and an ultrasonic probe 188 disposed at the tip thereof
is advanced through biopsy channel 178 until the catheter tip exits
therefrom, and the endoscope tip is further manipulated and the catheter
is further advanced until ultrasonic probe 188 comes to rest on the
visualized protrusion, such as protrusion 184. The ultrasonic field
provided by ultrasonic probe 188 may be either transverse to or parallel
to the longitudinal axis of tube 186. The probe may be constructed in a
manner similar to that illustrated in FIGS. 7A-7C or in the manner
discussed hereinafter in conjunction with FIGS. 10A, 10B and 11.
When the catheter is in place, the Doppler signal obtained therefrom is
monitored for that characteristic of venous flow. If such a Doppler signal
is obtained, the p | | |
