U.S. patent application number 10/616831 was filed with the patent office on 2004-06-03 for use of focused ultrasound for vascular sealing.
This patent application is currently assigned to Therus Corporation (Legal). Invention is credited to Perozek, David M., Weng, Lee, Zhang, Jimin.
Application Number | 20040106880 10/616831 |
Document ID | / |
Family ID | 26859662 |
Filed Date | 2004-06-03 |
United States Patent
Application |
20040106880 |
Kind Code |
A1 |
Weng, Lee ; et al. |
June 3, 2004 |
Use of focused ultrasound for vascular sealing
Abstract
An ultrasonic applicator unit (2) is used diagnostically to
locate a puncture wound (316) in an artery and then therapeutically
to seal the puncture wound with high intensity focused ultrasound
(HIFU). A control unit (6) coupled to the applicator unit includes
a processor (74) that automates the procedure, controlling various
parameters of the diagnostic and therapeutic modes, including the
intensity and duration of the ultrasonic energy emitted by the
applicator unit. A protective, sterile acoustic shell (4), which is
intended to be used with a single patient and then discarded, is
slipped over the applicator unit to protect against direct contact
between the applicator unit and the patient and to maintain a
sterile field at the site of the puncture. The apparatus and method
are particularly applicable to sealing a puncture made when
inserting a catheter into an artery or other vessel. Several
different procedures are described for locating the puncture wound,
including imaging the vessel in which the puncture is disposed and
use of a locator rod to determine the disposition of the puncture
along the longitudinal axis of the artery.
Inventors: |
Weng, Lee; (Bellevue,
WA) ; Perozek, David M.; (Mercer Island, WA) ;
Zhang, Jimin; (Bellevue, WA) |
Correspondence
Address: |
Attn: Sheldon K. Lee
Therus Corporation
Suite 200
2401 Fourth Avenue
Seattle
WA
98121
US
|
Assignee: |
Therus Corporation (Legal)
2401 Fourth Avenue; Suite 200
Seattle
WA
98121
|
Family ID: |
26859662 |
Appl. No.: |
10/616831 |
Filed: |
July 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10616831 |
Jul 10, 2003 |
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09696076 |
Oct 25, 2000 |
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6656136 |
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60163466 |
Oct 25, 1999 |
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60171703 |
Dec 23, 1999 |
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Current U.S.
Class: |
601/2 |
Current CPC
Class: |
G10K 11/346 20130101;
A61N 7/02 20130101; A61B 2562/164 20130101; A61B 2090/378 20160201;
A61B 2090/3904 20160201; G10K 11/32 20130101; A61B 2090/3937
20160201; A61B 2017/00907 20130101; A61B 17/0057 20130101; A61B
2017/00504 20130101; A61B 8/4422 20130101; A61B 2090/062 20160201;
A61B 2017/00641 20130101 |
Class at
Publication: |
601/002 |
International
Class: |
A61H 001/00 |
Claims
The invention in which an exclusive right is claimed is defined by
the following:
1. A method for closing a puncture in a vascular vessel of a
patient, comprising the steps of: (a) determining a site of the
puncture in the vascular vessel; (b) positioning an ultrasonic
transducer applicator at a position adjacent to the site that was
determined; (c) coupling the ultrasonic transducer applicator to a
control that includes a processor programmed to control
administration of ultrasonic energy to efficaciously seal a
puncture; and (d) enabling a user to initiate a process that is
controlled by the control, said control automatically controlling
the ultrasonic transducer applicator so that the ultrasonic energy
produced by the ultrasonic transducer applicator is focused at the
site and is administered to the site at a sufficient intensity and
duration to denature tissue at the puncture, closing and sealing
the puncture.
2. The method of claim 1, wherein the step of determining the site
of the puncture comprises the steps of: (a) generating an imaging
ultrasonic beam with the ultrasonic transducer applicator, said
imaging ultrasonic beam being transmitted into the patient
proximate an expected location for the site; (b) receiving a
reflection of the imaging ultrasonic beam from within the patient
with the ultrasonic transducer applicator, producing a
corresponding output signal; and (c) processing the output signal
with the processor in the control, to determine the site of the
puncture.
3. The method of claim 2, further comprising the step of providing
a visual indication of a location of the site of the puncture,
thereby enabling an operator to position the ultrasonic transducer
applicator so that the ultrasonic energy produced by the ultrasonic
transducer applicator is directed at the site of the puncture.
4. The method of claim 3, wherein the visual indication comprises
an image of the site in which an axis of the vascular vessel is
visually evident, and wherein the step of enabling the operator
further comprises the step of positioning the ultrasonic transducer
applicator longitudinally along the axis of the vascular vessel so
that the ultrasonic energy produced by the ultrasonic transducer
applicator is directed at the site of the puncture.
5. The method of claim 4, further comprising the step of providing
an object that extends from outside the patient into the
puncture.
6. The method of claim 5, wherein the step of positioning includes
the step of estimating the location of the puncture along the
longitudinal axis of the vessel based upon a disposition of the
object extending outside the patient.
7. The method of claim 5, wherein the visual indication comprises
an image of the site in which the object extending into the
puncture is evident, further comprising the step of estimating the
location of the puncture based upon a disposition of the object in
the image.
8. The method of claim 3, further comprising the steps of: (a)
processing the output signal with the processor to determine the
site of the puncture; (b) controlling an indicator disposed on the
ultrasonic transducer applicator to provide an indication of a
direction in which the ultrasonic transducer applicator should be
moved to be adjacent to the site of the puncture.
9. The method of claim 3, further comprising the step of using the
processor for automatically controlling at least one of a
direction, the intensity, and a focus of the ultrasonic energy, to
ensure that the ultrasonic energy is administered to the site of
the puncture.
10. The method of claim 9, wherein the processor directs the
ultrasonic energy so as to overscan the site of the puncture,
ensure that the puncture is closed and sealed.
11. The method of claim 10, wherein the processor moves the focus
of the ultrasonic energy while administering the ultrasonic energy,
to overscan the site of the puncture.
12. The method of claim 1, wherein an ultrasound emitter of the
ultrasonic transducer applicator has an aspheric shape so that the
ultrasonic energy that is directed at the site of the puncture
overscans the site, thereby ensuring the ultrasonic energy is
applied to the site of the puncture.
13. The method of claim 2, wherein the ultrasonic transducer
applicator uses a common array of transducers for generating both
the imaging ultrasound beam and the ultrasound energy that closes
and seals the puncture.
14. The method of claim 2, further comprising the step of
interrupting the administration of the ultrasonic energy to again
generate the imaging ultrasound beam, thereby confirming whether
the ultrasonic energy is being directed at the site of the
puncture.
15. The method of claim 1, further comprising the step of employing
the processor to control a force applied against a surface of the
patient with a force generator included in the ultrasonic
transducer applicator, said force being controlled so that a
pressure developed by said force is sufficient to substantially
stop fluid leakage from the vascular vessel, but not so great as to
substantially occlude fluid flow through the vascular vessel.
16. The method of claim 1, further comprising the step of enclosing
a ultrasonic transducer within a protective shell to provide the
ultrasonic transducer applicator, said protective shell being
adapted to contact an external dermal portion of the patient in
order to convey the ultrasonic energy transdermally to the site of
the puncture and protecting against a direct contact between the
ultrasonic transducer and the external dermal portion of the
patient.
17. A method for closing a puncture in a vascular vessel of a
patient, comprising the steps of: (a) determining a site of the
puncture in the vascular vessel; (b) providing a protective
applicator shell for an ultrasonic transducer; (c) mating the
ultrasonic transducer with the protective applicator shell to
provide an ultrasonic transducer applicator; (d) positioning the
ultrasonic transducer applicator externally on the patient,
adjacent to the site determined for the puncture in the vascular
vessel; (e) energizing the ultrasonic transducer applicator to
administer ultrasonic energy to the puncture in the vascular
system, said ultrasonic energy denaturing tissue at the puncture,
closing and sealing the puncture.
18. The method of claim 17, further comprising the step of removing
a cover overlying a gel disposed on a face of the protective
applicator shell prior to the step of positioning the ultrasonic
transducer, said gel providing an ultrasonic coupling interface
between the ultrasonic transducer and a dermal surface of the
patient through which the ultrasonic energy is conveyed.
19. The method of claim 17, wherein the step of determining the
site of the puncture comprises the steps of: (a) generating an
imaging ultrasonic beam with the ultrasonic transducer applicator,
said imaging ultrasonic beam being transmitted into the patient
proximate an expected location for the site; (b) receiving a
reflection of the imaging ultrasonic beam from within the patient
with the ultrasonic transducer applicator, producing a
corresponding output signal; and (c) using the output signal to
determine the site of the puncture.
20. The method of claim 19, further comprising the step of
providing a visual indication of a location of the site of the
puncture, thereby enabling an operator to position the ultrasonic
transducer applicator so that the ultrasonic energy produced by the
ultrasonic transducer applicator is directed at the site of the
puncture.
21. The method of claim 20, wherein the visual indication comprises
an image of the site in which an axis of the vascular vessel is
visually evident, and wherein the step of enabling the operator
further comprises the step of positioning the ultrasonic transducer
applicator longitudinally along the axis of the vascular vessel so
that the ultrasonic energy produced by the ultrasonic transducer
applicator is directed at the site of the puncture.
22. The method of claim 21, further comprising the step of
providing an object that extends from outside the patient into the
puncture.
23. The method of claim 22, wherein the step of positioning
includes the step of estimating the location of the puncture along
the longitudinal axis of the vessel based upon a disposition of the
object extending outside the patient.
24. The method of claim 22, wherein the visual indication comprises
an image of the site in which the object extending into the
puncture is evident, further comprising the step of estimating the
location of the puncture based upon a disposition of the object in
the image.
25. The method of claim 17, further comprising the step of
overscanning the site of the puncture with the ultrasonic energy to
ensure that the ultrasonic energy is administered to the seal the
puncture.
26. The method of claim 19, wherein the ultrasonic transducer
applicator uses a common array of transducers for generating both
the imaging ultrasound beam and the ultrasound energy that closes
and seals the puncture.
27. The method of claim 19, further comprising the step of
interrupting the administration of the ultrasonic energy when
sealing the puncture to again generate the imaging ultrasound beam,
thereby confirming whether the ultrasonic energy is being directed
at the site of the puncture.
28. The method of claim 17, further comprising the step of
activating a force generator included within the ultrasonic
transducer applicator to produce a pressure applied against a
dermal layer of the patient over the site of the puncture.
29. The method of claim 28, further comprising the step of
providing an indication that the pressure being applied to the site
of the puncture is sufficient to substantially prevent a fluid from
leaking from the vascular vessel, but not so great as to
substantially occlude a fluid flow through the vascular vessel.
30. Apparatus adapted to seal a puncture in a vascular vessel of a
patient, comprising: (a) an ultrasonic transducer applicator that
controllably radiates ultrasonic energy and which is adapted to:
(i) couple the ultrasonic energy into a body of a patient; (ii)
controllably focus the ultrasonic energy on a puncture disposed in
a vascular vessel of a patient; and (iii) administer the ultrasonic
energy to the site at an intensity sufficient to denature tissue,
closing and sealing the puncture; and (b) a controller that is
coupled to the ultrasonic transducer applicator, said controller
including a processor and a memory in which are stored machine
instructions, said machine instructions, when executed by the
processor, causing it to control a plurality of parameters
affecting administration of the ultrasonic energy to the site by
the ultrasonic transducer applicator, said parameters being
controlled by the processor so as to efficaciously close and seal a
puncture in a vascular system of a patient.
31. The apparatus of claim 30, further comprising a display coupled
to the controller, said ultrasonic transducer applicator being
controlled by the controller to produce an imaging ultrasonic beam
adapted to be transmitted into a patient proximate an expected
location for the site of the puncture, said ultrasonic transducer
applicator producing an output signal in response to receiving a
reflection of the imaging ultrasonic beam, said output signal being
used to provide an image on the display useful for determining the
site of a puncture.
32. The apparatus of claim 31, further comprising an object that is
adapted to be introduced into a puncture and to extend externally,
said object providing a visual indication of a location of a site
of a puncture.
33. The apparatus of claim 32, wherein the object is at least in
part formed of a material that is clearly visually evident on the
display, to assist in determining a site of a puncture.
34. The apparatus of claim 33, wherein a portion of the object
adapted to be disposed at a puncture comprises a material that is
more visually evident on the display than other portions of the
object, to assist in determining a site of a puncture.
35. The apparatus of claim 30, wherein the ultrasonic transducer
applicator includes an indicator that is coupled to the controller,
said controller responding to the output signal to provide a visual
indication with the indicator, said visual indication denoting a
direction in which the ultrasonic transducer applicator should be
moved to enable the ultrasonic energy to be more accurately
directed at a puncture site.
36. The apparatus of claim 30, wherein the processor automatically
controls at least one of a direction, an intensity, and a focus of
the ultrasonic energy, to ensure that the ultrasonic energy is
administered to a site of a puncture.
37. The apparatus of claim 36, wherein the machine instructions
executed by the processor control the ultrasonic transducer
applicator to direct the ultrasonic energy so as to overscan a site
of a puncture, to ensure that a puncture is closed and sealed
thereby.
38. The apparatus of claim 36, wherein the machine instructions
executed by the processor control the ultrasonic transducer
applicator to shift a focus of the ultrasonic energy to overscan a
site of a puncture.
39. The apparatus of claim 30, wherein the ultrasonic transducer
applicator includes an emitter face having an aspheric shape so
that the ultrasonic energy emitted thereby is focused to encompass
an area substantially greater than a site of a puncture, to ensure
that the ultrasonic energy is applied to a puncture.
40. The apparatus of claim 31, wherein the ultrasonic transducer
applicator includes an ultrasound emitter that is controlled by the
processor in accord with the machine instructions to emit both the
ultrasound energy employed to close and seal a puncture and the
imaging ultrasound beam that is used to determine a site of a
puncture.
41. The apparatus of claim 31, wherein the machine instructions
executed by the processor further cause the processor to interrupt
administration of the ultrasonic energy to a site of a puncture to
generate the imaging ultrasonic beam, for again displaying an image
to confirm whether the ultrasonic energy is being accurately
directed to a site of a puncture.
42. The apparatus of claim 30, wherein the ultrasonic transducer
applicator further comprises a force generator that produces a
pressure controlled by the processor in accord with the machine
instructions executed by the processor.
43. The apparatus of claim 42, further comprising a force sensor
that monitors a force being applied against a surface of a patient,
producing a signal indicative thereof that is coupled to the
control, said control employing the signal to vary a pressure
caused by the force generator so that the pressure is sufficient to
substantially prevent a fluid leaking from a puncture, but not so
great as to substantially occlude a fluid flow through a vascular
vessel in which a puncture is disposed.
44. The apparatus of claim 30, wherein the ultrasonic transducer
applicator comprises an ultrasonic emitter face and a protective
shell adapted to contact an external dermal portion of a patient in
order to convey the ultrasonic energy transdermally to a site of a
puncture, while protecting against the ultrasonic emitter face
directly contacting an external dermal portion of a patient.
45. Apparatus adapted to seal a puncture in a vascular vessel of a
patient, comprising: (a) an ultrasonic transducer that controllably
radiates ultrasonic energy and which is adapted to: (i)
controllably focus the ultrasonic energy on a site where a puncture
is disposed in a vascular system of a patient; and (ii) generate
ultrasonic energy at an intensity sufficient to denature tissue,
closing and sealing a puncture; and (b) a protective applicator
shell sized to fit over the ultrasonic transducer and including a
facing surface adapted to contact an external surface of a
patient's body at the site where a transdermal puncture extends
into a vascular vessel of a patient, said protective applicator
shell coupling the ultrasonic generated by the ultrasonic
transducer into a patient's body at the site and protecting against
the ultrasonic transducer directly contacting a patient while a
puncture is being closed and sealed by the ultrasonic energy.
46. The apparatus of claim 45, wherein the protective applicator
shell includes an outer surface on which is disposed a patch of a
gel covered by a removable tab, said patch of the gel being exposed
upon removal of the tab to facilitate coupling of the ultrasound
energy into a body of a patient.
47. The apparatus of claim 45, wherein the protective applicator
shell includes an interior cavity into which the ultrasonic
transducer is inserted, said cavity including a layer of a gel to
facilitate coupling of the ultrasonic energy produced by the
ultrasonic transducer into a surface with which the protective
applicator shell is in contact.
48. The apparatus of claim 45, wherein the ultrasonic transducer
includes a cable, said protective applicator shell being provided
for use in a sterile state and including a protective sheath that
is adapted to prevent the cable from contacting a sterile field on
a body of patient against which the protective applicator shell is
brought into contact to administer the ultrasonic energy.
49. The apparatus of claim 45, wherein the ultrasonic transducer is
adapted to selectively generate a broad imaging beam and a focused
beam for administering the ultrasonic energy to a puncture site,
said broad imaging beam being used to determine a location of a
site of a puncture in a vascular vessel.
50. The apparatus of claim 45, wherein the protective applicator
shell is substantially optically transparent to enable markings and
indicators included on the ultrasonic transducer to be observed by
an operator using the ultrasonic transducer while the ultrasonic
transducer is fitted inside the protective applicator shell.
Description
RELATED APPLICATIONS
[0001] This application is based on prior copending U.S.
provisional patent application Serial No. 60/163,466, filed Oct.
25, 1999, and prior copending U.S. provisional patent application
Serial No. 60/171,703, filed Dec. 23, 1999, the benefit of the
filing dates of which is hereby claimed under 35 U.S.C. .sctn.
119(e).
FIELD OF THE INVENTION
[0002] The present invention generally relates to methods and
apparatus for sealing vascular punctures and wounds, and more
particularly, to a device that may be used to deliver ultrasound
energy to a vascular puncture site to arrest bleeding.
BACKGROUND OF THE INVENTION
[0003] Various surgical procedures are performed by medical
specialists such as cardiologists and radiologists, utilizing
percutaneous entry into a blood vessel. To facilitate
cardiovascular procedures, a small gauge needle is introduced
through the skin and into a target blood vessel, often the femoral
artery. The needle forms a puncture through the blood vessel wall
at the distal end of a tract that extends through the overlying
tissue. A guide wire is then introduced through the bore of the
needle, and the needle is withdrawn over the guide wire. An
introducer sheath is next advanced over the guide wire; the sheath
and guide wire are left in place to provide access during
subsequent procedure(s). The sheath facilitates passage of a
variety of diagnostic and therapeutic instruments and devices into
the vessel and its tributaries. Illustrative diagnostic procedures
include angiography, intravascular ultrasonic imaging, and the
like; exemplary interventional procedures include angioplasty,
atherectomy, stent and graft placement, embolization, and the like.
After this procedure is completed, the catheters, guide wire, and
introducer sheath are removed, and it is necessary to close the
vascular puncture to provide hemostasis and allow healing.
[0004] The most common technique for achieving hemostasis is to
apply hard pressure on the patient's skin in the region of the
tissue tract and vascular puncture to form a blood clot. Initially,
pressure is applied manually and subsequently is maintained through
the use of mechanical clamps and other pressure-applying devices.
While effective in most cases, the application of external pressure
to the patient's skin presents a number of disadvantages. When
applied manually, the procedure is time-consuming and requires the
presence of a medical professional for thirty minutes or more. For
both manual and mechanical pressure application, the procedure is
uncomfortable for the patient and frequently requires the
administration of analgesics to be tolerable. Moreover, the
application of excessive pressure can occlude the underlying
artery, resulting in ischemia and/or thrombosis. Even after
hemostasis has apparently been achieved, the patient must remain
immobile and under observation for hours to prevent dislodgment of
the clot and to assure that bleeding from the puncture wound does
not resume. Renewed bleeding through the tissue tract is not
uncommon and can result in hematoma, pseudoaneurisms, and
arteriovenous fistulas. Such complications may require blood
transfusion, surgical intervention, or other corrective procedures.
The risk of these complications increases with the use of larger
sheath sizes, which are frequently necessary in interventional
procedures, and when the patient is anticoagulated with heparin or
other drugs.
[0005] In recent years, several hemostasis techniques have been
proposed to address the problem of sealing vessel wall punctures
following percutaneous transcatheter procedures. Related prior art
is described in U.S. Pat. Nos. 5,320,639; 5,370,660; 5,437,631;
5,591,205; 5,830,130; 5,868,778; 5,948,425; 6,017,359; and
6,090,130. In each of these patents, bioabsorbable, thrombogenic
plugs comprising collagen and other materials are placed proximal
to the vessel wall puncture site to stop bleeding. The large
hemostasis plug stimulates blood coagulation in the vessel puncture
site, but blocks the catheter entry tract, making catheter reentry
more difficult, if required.
[0006] Other related prior art disclosed in U.S. Pat. Nos.
5,707,393; 5,810,884; 5,649,959; and 5,350,399 provides for the use
of small dissolvable disks or anchors that are placed in the vessel
to block or clamp the puncture hole. However, any device remaining
in the vessel lumen increases the risk of thrombus formation. Such
a device also can detach and cause occlusion in a distal blood
vessel, which would likely require major surgery to remove.
[0007] Additional prior art includes U.S. Pat. Nos. 5,779,719;
5,496,332; 5,810,850; and 5,868,762. In the disclosure of these
patents, needles and sutures delivered through catheters are used
to ligate the puncture. The suturing procedure requires particular
skill. Suture material left in the vessel may cause tissue
irritation that will prolong the healing process.
[0008] Still other prior art is disclosed in U.S. Pat. No.
5,626,601, wherein a procoagulant is injected into the puncture,
with a balloon catheter blocking inside the vessel lumen. However,
in some cases, the clotting agent may leak past the balloon into
the vessel lumen and cause stenosis.
[0009] Yet other prior art references related to this topic include
U.S. Pat. Nos. 4,929,246; 5,810,810; and 5,415,657, which disclose
the use of a laser or of radio-frequency (RF) energy that is
transmitted to the blood vessel through a catheter to thermally
fuse or weld the punctured tissue together.
[0010] All of the above cited prior art references require either
introducing and leaving foreign objects in the patient's body,
and/or inserting a tubular probe of large diameter into the tissue
channel left by the catheter in order to seal the puncture.
[0011] As will be evident from the preceding discussion, there is a
clear need for an improved method and apparatus for sealing a
puncture left in a blood vessel, following an intravascular
catheterization procedure. The method and apparatus should cause
rapid cessation of bleeding, not rely on blood clot formation, and
should be independent of the patient's coagulation status. By
employing such a method and apparatus, the patient will be more
comfortable as a result of shortened hemostasis and ambulation
times, and physician and hospital resources will thereby be
minimized. In addition, the method and apparatus should not leave
any foreign object in the patient's body, to reduce the risk of
stenosis at or distal to the puncture wound. An ideal device will
be noninvasive and should not include any component that must be
inserted in the catheter tract and which might further damage the
wound and impede the sealing process.
SUMMARY OF THE INVENTION
[0012] In accord with the present invention, a method and apparatus
are defined that provide advantageous solutions to the problem of
expeditiously and safely sealing vascular catheter entry wounds
made in connection with medical procedures. The method includes the
steps of determining a site of the puncture in the vascular vessel
and positioning an ultrasonic transducer applicator at a position
adjacent to the site. The ultrasonic transducer applicator is
coupled to a control that includes a processor programmed to
administer ultrasonic energy in a manner that efficaciously seals a
puncture. A user is enabled to initiate a process that is
controlled by the control, so that very little operator training is
required. The control automatically controls the ultrasonic
transducer applicator so that the ultrasonic energy produced by the
ultrasonic transducer applicator is focused at the site and is
administered at a sufficient intensity and duration to denature
tissue at the puncture, closing and sealing the puncture.
[0013] To determine the site of the puncture, an imaging ultrasonic
beam is generated with the ultrasonic transducer applicator and is
transmitted into the patient, proximate an expected location for
the site. A reflection of the imaging ultrasonic beam is then
received from within the patient using the ultrasonic transducer
applicator, producing a corresponding output signal. The output
signal is processed with the processor included in the control to
facilitate determining the site of the puncture.
[0014] For example, a visual indication of a location of the site
of the puncture can be provided to enable an operator to position
the ultrasonic transducer applicator so that the ultrasonic energy
produced by the ultrasonic transducer applicator is directed at the
site. Such a visual indication may be in the form of, for example,
lighted display indicators. In one form of the present invention,
the visual indication includes an image of the site in which an
axis of the vascular vessel is visually evident, enabling the
operator to position the ultrasonic transducer applicator
longitudinally along the axis of the vascular vessel so that the
ultrasonic energy is directed at the site of the puncture.
[0015] In an alternative embodiment, an object is provided that
extends into the puncture from outside the patient. The operator
can then estimate the location of the puncture along the
longitudinal axis of the vessel based upon a disposition of the
object extending outside the patient. As yet a further alternative,
the visual indication includes an image of the site in which the
object extending into the puncture is evident. An estimate is made
of the location of the puncture based upon a disposition of the
object in the image.
[0016] Finally, the output signal can be processed with the
processor to determine the site of the puncture. An indicator
disposed on the ultrasonic transducer applicator can be controlled
by the processor to provide an indication of a direction in which
the ultrasonic transducer applicator should be moved to position it
adjacent to the site of the puncture.
[0017] The processor is preferably used for automatically
controlling at least one of a direction, an intensity, and a focus
of the ultrasonic energy, to ensure that the ultrasonic energy is
administered to the site of the puncture. Using the processor, the
ultrasonic energy is directed so as to overscan the site of the
puncture, ensuring that the puncture is closed and sealed. For
example, the processor can move the focus of the ultrasonic energy
while it is being administered, to overscan the site of the
puncture. As another alternative, an ultrasound emitter of the
ultrasonic transducer applicator has an aspheric shape so that the
ultrasonic energy that is directed at the site of the puncture
covers a larger area that overscans the site. Other transducer
configurations that provide a laterally broadened focal region may
also be employed.
[0018] Preferably, the ultrasonic transducer applicator uses a
common array of transducers for generating both the imaging
ultrasound beam and the ultrasound energy that closes and seals the
puncture.
[0019] It is also contemplated that the administration of the
ultrasonic energy be interrupted, to again generate the imaging
ultrasound beam, thereby confirming whether the ultrasonic energy
is being directed at the site of the puncture.
[0020] The processor is preferably employed to control a force
applied against a surface of the patient using a force generator
included in the ultrasonic transducer applicator. This force is
controlled so that a pressure developed by the force is sufficient
to substantially stop fluid leakage from the vascular vessel, but
not so great as to substantially occlude fluid flow through the
vascular vessel.
[0021] Another aspect of the invention is directed to enclosing the
unit applicator within a protective, acoustic coupling shell. The
protective, acoustic coupling shell is adapted to contact an
external dermal portion of the patient in order to convey the
ultrasonic energy transdermally to the site of the puncture, while
isolating an ultrasonic emitter surface on the ultrasonic
transducer from direct, contacting exposure to the patient. The
protective, acoustic coupling shell is preferably pre-sterilized
and preferably includes a gel patch on an outer surface that is
protected by a tab. The tab is removed prior to contacting the
external dermal surface of the patient.
[0022] Still another aspect of the present invention is directed to
apparatus. The apparatus include elements that carry out functions
generally consistent with the steps of the method discussed
above.,
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0023] The foregoing aspects and many of the attendant advantages
of this invention will become more readily appreciated as the same
becomes better understood by reference to the following detailed
description, when taken in conjunction with the accompanying
drawings, wherein:
[0024] FIG. 1 is a schematic block diagram of the primary
components employed in a preferred embodiment of the present
invention;
[0025] FIG. 2 is a schematic diagram illustrating how the present
invention is employed for sealing a puncture in a vessel;
[0026] FIG. 3 schematically illustrates a collagen seal produced by
the present invention to close the puncture in the vessel of FIG.
2;
[0027] FIG. 4 is a flow chart illustrating the logical steps
followed during sealing of a vascular wound in accord with the
present invention;
[0028] FIG. 4A is a flow chart illustrating the optional steps
employed for detecting nerves during the method of FIG. 4;
[0029] FIG. 5 is a cross-sectional view of a portion of a patient's
body, illustrating an applicator unit in accord with the present
invention disposed adjacent to a puncture that extends
transdermally into an artery;
[0030] FIG. 6 is a cutaway isometric view of the applicator shown
in FIG. 5;
[0031] FIG. 6A is an isometric view showing the force sensing
transducer, force generator, and ultrasonic array of the
applicator;
[0032] FIG. 7 is an elevational view of a locator rod adapted to be
inserted into a puncture wound over a guide wire;
[0033] FIG. 7A is a cross-sectional view of a portion of a
patient's body like that in FIG. 5, illustrating the locator rod of
FIG. 7 being used to determine a location of a puncture in the
artery relative to the applicator unit;
[0034] FIG. 7B is similar to FIG. 7A, but illustrates the use of
ultrasonic pulse-echo techniques to determine the spatial location
of the locator rod;
[0035] FIG. 7C depicts a view of a framed two-dimensional image a
target region generally orthogonal to that shown in FIG. 7A and
FIG. 7B, for use in locating the puncture site;
[0036] FIG. 8 is a schematic isometric view of an embodiment of the
applicator that uses a disposable shell;
[0037] FIG. 8A is an side view of the disposable shell of FIG.
8;
[0038] FIG. 9 is a schematic system block diagram depicting modules
included in the applicator and control unit;
[0039] FIGS. 10 and 10A respectively illustrate the ultrasound beam
orientation relative to the vessel from the side of the vessel and
as viewed along the vessel;
[0040] FIG. 11 is a plan view of an embodiment of the applicator
illustrating the controls and indicators that it includes;
[0041] FIGS. 12 and 12A respectively illustrate the side and
longitudinal geometry of the therapeutic ultrasound beam; and
[0042] FIG. 13 is an isometric view illustrating the ultrasound
beam geometry produced by an aspheric transducer.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0043] Use of Ultrasound for Sealing Punctures
[0044] Because of its unique properties in soft tissue, ultrasound
can be brought to a tight focus at a distance from its source. If
sufficient energy is radiated within the ultrasound beam, cells
located in the focal volume can be rapidly heated, while
intervening and surrounding tissues are spared. Surrounding tissues
are unaffected in the unfocused portion of the ultrasound beam
because the energy is spread over a correspondingly larger area and
associated heating is minimized.
[0045] Whereas ultrasound intensities on the order of 0.1
Watts/cm.sup.2 are employed in diagnostic imaging applications,
intensities in excess of 1,000 Watts/cm.sup.2 are typical in
high-intensity focused ultrasound (HIFU) applications. At the focal
point, these high intensities result in large, controlled
temperature rises within a matter of seconds.
[0046] It has been demonstrated in numerous in vivo animal studies
that HIFU can rapidly seal blood vessel punctures and lacerations
over a wide range of sizes. When accurately targeted on a vascular
wound, ultrasound has been shown to induce complete hemostasis in
less than one minute in the femoral, carotid, and axillary
arteries, and in the femoral and jugular veins of large animals,
while blood flow through the treated vessels remained unaffected.
These investigations included: (a) sealing punctured, surgically
exposed vessels using visual targeting, (b) sealing incised,
surgically exposed vessels using visual targeting, (c) sealing
surgically exposed, punctured vessels using Doppler-guided
ultrasound targeting, and (d) noninvasive sealing of punctured
vessels under ultrasound imaging guidance wherein complete
hemostasis was noted in 13.+-.12 seconds.
[0047] The mechanism of hemostasis in these ultrasound-exposed
vascular wounds appears thermal in origin and involves
denaturization of native perivascular collagen with subsequent
formation of an extensive fibrin network that covers the hole,
thereby sealing it closed. The fibrin links with adjacent vessel
wall tissues to form a seal that has been shown to be independent
of puncture hole size. Acoustic streaming forces generated by the
HIFU beam were also observed to play a role in opposing the escape
of blood from the vascular wound. Blood clotting is not believed to
be a factor in achieving acoustic hemostasis, as evidenced by
equally rapid and complete wound sealing in highly anticoagulated
animals and in ex vivo vessels in which saline has been substituted
for blood.
[0048] Overview of the Present Invention
[0049] FIGS. 1 and 2 show the main components of an ultrasonic
system suitable for use in implementing the present invention. As
illustrated in FIG. 1, a hand-held applicator unit 2 is positioned
over an arterial wound 8 in the patient. Included with the
hand-held applicator unit is a generally single-use, pre-sterilized
cover and acoustic coupling shell 4 that slips over applicator 2. A
control unit 6 implements algorithms to facilitate the method and
is coupled to applicator 2.
[0050] The user enters various conventional scan and control
parameters into an input unit 70, which typically includes user
input devices 72. Examples of such devices include a keyboard,
knobs, and buttons. The input unit is connected to a processing
system 74, which will typically comprise a plurality of
microprocessors and/or digital signal processors. Processing system
74 may, however, also be implemented using a single processor of
sufficient speed to handle the various tasks described below. A
conventional memory 75 will normally be included in the system to
store, among other data, transmission control parameters and
imaging data generated in any given implementation of the present
invention.
[0051] Processing system 74 sets, adjusts, and monitors the
operating parameters of a conventional transmission and control
circuit 76. Control circuit 76 forms a transmit ultrasonic waveform
by generating and applying electrical control and driving signals
to an ultrasound transducer 78, which preferably comprises an array
of individually controllable piezoelectric elements. As is well
known in the art, the piezoelectric elements generate ultrasonic
waves when electrical signals of a proper frequency are applied to
them; conversely, when receiving reflected ultrasonic waves, they
generate electrical signals corresponding to the mechanical
vibrations caused by the returning ultrasonic waves.
[0052] Transducer 78 is positioned against a portion 82 of the body
of a patient, and by varying the phasing, amplitude, and timing of
the driving signals for the transducer array elements, ultrasonic
waves are focused to form a transmit beam 314 of high-intensity
ultrasound.
[0053] In FIG. 2, open arrows indicate the direction of a flow of
blood within a blood vessel 312, which has a puncture site 316 that
may have been caused by introduction of a catheter or, in the case
of unintended punctures that have produced wounds, by some other
object. The tissue forming a layer 318 of collagen found on the
surface of blood vessels is also shown in FIG. 2 surrounding blood
vessel 312.
[0054] As will be clear from the description of the present
invention below, it is not necessary for the system to include an
imaging capability. However, the provision of an imaging
capability, including pulse-echo lines of interrogation that are
not displayed as images, in the present invention should assist a
user to more accurately locate a vascular puncture site. It is
recognized that a full display of the insonified vascular target
site is not required.
[0055] Nonetheless, since imaging of a vascular target site is
preferable and will employ echo processing (especially, Doppler),
FIG. 2 also illustrates a reception controller 78, which will
include conventional amplification and signal conditioning
circuitry as needed. Reception controller 88, all or part of which
is normally integrated into processing system 74, converts the
ultrasonic echo signals (which are typically at radio frequencies,
on the order of a few to tens of megahertz) into lower frequency
ranges for processing and may also include analog-to-digital
conversion circuitry. The processing includes, as needed, such
known signal conditioning as time-gating, gain compensation,
Doppler frequency shift processing, and diffraction compensation,
in order to identify echo signals from any selected focal region.
The type of conventional signal processing needed (if any) will in
general depend on the particular implementation of the present
invention employed and can be implemented using known design
methods.
[0056] Note that it is not essential, according to the present
invention, that the transducer 78 be used externally, relative to
the patient's body. It is also contemplated that the transducer may
be maneuvered inside a patient's body, and the beam focused on a
puncture from inside the body. For example, a transesophageal
probe, laparoscopic, or other probe inserted into a body cavity,
such as the vagina or rectum can be used to practice the present
invention. A suitably designed probe inserted into an open body
cavity or via minimally invasive means could be used to arrest
bleeding in surgical or trauma care situations. Yet, most of the
following discussion is directed to a preferred embodiment of the
present invention in which the transducer is intended to be used
externally, since an initial commercial product in accord with the
present invention will be designed for such use.
[0057] A conventional display system 92 may also be included in
order to display information concerning transmission power, time,
focus data, etc. The display system will include known circuitry
for scan conversion and for driving the display, as needed. These
circuits are well known and therefore need not be specifically
illustrated or described further to provide an enabling
disclosure.
[0058] FIG. 3 illustrates the result of an insonification of
puncture site 316 using the present invention. As the focal point
of transmit beam 314 (see FIG. 2) is moved around (as illustrated
by the arrows pointing in either direction from the focus of the
beam) the area of puncture site 316 using conventional
beam-steering techniques, the tissue adjacent the puncture site 316
will denature. In effect, the collagen in the tissue "melts" and
flows over and into the puncture opening. When the collagen cools,
it forms a "patch" that not only covers the puncture, but also
flows partially into the puncture opening in the wall of the blood
vessel. Moreover, since the denatured tissue tends to contract, it
also tends to pull the edges of the puncture together and thus
further close the wound.
[0059] It should be noted that the present invention can be
employed to seal vascular wounds of various types and is not
limited to the type of wound created as a result of interventional
procedures in which a catheter has been introduced into a vascular
vessel. As noted above, application of thermal treatment to the
tissue overlying a wound has been demonstrated to seal the wound.
In the present invention, a practical method has been developed for
repeatedly and reliably achieving sealing of the puncture in a
vascular vessel. Steps carried out in this method are shown in FIG.
4, which is discussed below. These steps represent one preferred
embodiment of the present invention, but do not represent all
alternatives that might be employed to achieve acceptable
sealing.
[0060] Key steps in the method for vascular sealing described here
include:
[0061] 1. Positioning an ultrasound generating source on a patient
such that the source is targeted at an area including the wound to
be sealed;
[0062] 2. Applying a pressure against the patient in an area
overlying the wound and directed substantially toward the vessel to
be treated;
[0063] 3. While the pressure and the positioning of the ultrasound
source are maintained, carrying out an insonification of a volume
of tissue that includes the wound, using an ultrasound exposure
that delivers an acoustic energy density (measured at the
approximate location of the wound), in excess of 100 joules/sq. cm,
but generally less than several thousand joules/sq. cm.
[0064] Additional steps of the method described below employ the
apparatus in an automated manner that facilitates ease of use and
ensures the safety and consistency of the results obtained.
[0065] A clinically acceptable device for sealing a puncture wound
in accord with the present invention must meet a number of
requirements, including:
[0066] 1. The device and associated procedure must be safe to use
in that they avoid undesirable bioeffects, so that the patient is
not injured directly or indirectly as a result of the procedure;
also, in the event that effective vessel sealing does not occur as
desired, traditional methods of applying pressure to the wound are
sufficient to accomplish hemostasis;
[0067] 2. The device and associated procedure must be easy to use
in an efficient manner, to facilitate proper, repeatable execution
of the sealing process; requirements for operator training should
be minimized;
[0068] 3. The sealing process must be sufficiently fast to enable
the entire procedure to be rapidly completed--preferably, in less
than 5 minutes;
[0069] 4. The cost per sealing procedure should be minimized;
and,
[0070] 5. The efficacy of the device should be very high, generally
achieving a success rate in excess of about 95%; acceptability of
the present invention in routine clinical practice does not permit
an unpredictable outcome.
[0071] These requirements are met by the present invention, as
described below, and as defined in the claims that follow. A
preferred embodiment of the device includes the components shown in
FIGS. 1 and 2, which were described above.
[0072] FIG. 6 and FIG. 6A show one preferred embodiment of
applicator unit 2. The applicator unit includes an outer housing 10
having an ergonomically considered shape so that it can be
conveniently hand held. The outer housing is best fabricated from
an injection moldable plastic material such as ABS or the like. The
operator grasps the outer housing of the applicator unit so as to
enable a control push-button 14 to be accessible and indicators 12,
16 and 30, 32, 34, and 36 to be visible to the operator.
Positioning the applicator unit at the appropriate location over
the wound area and activation of an essentially automated treatment
cycle are readily accomplished. The operator simply refers to the
indicators to determine when the applicator unit is properly
positioned and ready for use. Indicators 12 and 16 are used to
indicate when alignment of the applicator unit with the
longitudinal axis of the vessel to be sealed has been achieved.
Indicators 30, 32, 34, and 36 display the state of operation and
instruct the operator with respect to holding the applicator in
place as described in detail later in this description. Control 14
when pressed, activates the treatment cycle, thus initiating a
sequence of operations that determine ultrasonic scan parameters
(exposure time, scan pattern, intensity, focal range, etc.).
[0073] As shown in FIG. 6A, ultrasonic array assembly 20 is held
within outer housing 10 on a shaft 40, in a bearing assembly within
a force transducer 18, so as to permit movement of the ultrasonic
array assembly to and away from patient 8. Shaft 40 passes through
the bearing assembly provided within a force generator 18 and
terminates at a contacting force sensing transducer 42. Force
generator 18 comprises an electromagnetic solenoid that is rigidly
supported and mounted within housing 10 by structural members 46.
The face of ultrasonic array assembly 20 is in contact with the
appropriate location on the body of the patient (overlying the site
of the puncture) and is thus capable of applying a substantially
compressive, controllable force on the tissue structures with which
it is in contact. The force applied by the ultrasonic array
assembly is produced at least in part by controllably energizing
force generator 18. Ultrasonic array assembly 20 preferably
operates in a multiplicity of modes; however, separate ultrasonic
transducers can instead be provided for some or all of the
functions performed in a different design within the scope of the
present invention.
[0074] In the illustrated preferred embodiment, electrical
connections comprising wires 26 are routed within the outer housing
10 and out in a sealed bushing 44 that mounts a cable 28 to the
control unit 6. Cable 28 is sufficiently long, on the order of 10
feet in length, so that the control unit may be conveniently
located at a distance from the patient and operator location.
[0075] Applicator unit housing 10 is shaped to be used with a
slip-on, generally single-use protective applicator shell 4
(illustrated schematically in FIG. 1). The shell employed in the
preferred embodiment is shown in greater detail in FIGS. 8 and 8A.
Shell 4 has side walls 54 that are fabricated from a generally
optically transparent, semi-rigid plastic material. A skirt 52
extends from the rear of the shell and is pleated so that in
preparing for use of the applicator unit, an operator can grasp the
skirt and extend it sufficiently to protect a sterile area of the
patient from coming into contact with cord. The protective shell is
packaged in a sterile condition. The shell is fabricated from a
flexible plastic material having low acoustic absorption
characteristics. A fiducial mark 56 is provided on a side of the
applicator unit and visible through the optically transparent
material of the protective shell. This fiducial mark is employed to
visually align the applicator unit with a position on the patient
at which the applicator unit will be used to seal a puncture.
[0076] Sterile, generally gas free acoustic coupling gel 62 is
deposited in a patch on the bottom of flexible bottom 58. Prior to
use, the gel is held in place and sealed by semi-sticky adhesive
coated tab 60. Tab 60 is removed by the operator just prior to use,
thereby exposing the gel so that it provides a good acoustic
coupling with the surface of the patient's body. Protective
applicator shell 4 thus provides a sterile barrier over the
multi-use applicator unit and conveniently provides a
pre-determined amount of a specific appropriate acoustic coupling
medium. Although not shown, it is contemplated that the bottom of
the interior cavity of the shell may also include a layer of
acoustic coupling gel to ensure good acoustic coupling between the
applicator unit through the protective, applicator coupling
shell.
[0077] With reference to FIG. 1, applicator unit 2 is connected to
control unit 6. Power supplies, signal processing components, and
control and RF power generation components are housed within
control unit 6. FIG. 9 is a system block diagram illustrating the
modules disposed, in the preferred embodiment, within the
applicator unit 2 (i.e., the component shown within the dotted line
portion of this Figure) as well as the modules (all other modules
that are not in the applicator unit) disposed in the control unit
6. In this preferred embodiment, control unit 6 is packaged in a
small, self-contained pole- or cart-mounted enclosure that derives
its input power from a standard AC line power service (not shown).
Power supplies with the unit are designed to assure low leakage
currents for patient safe operation.
[0078] In the preferred embodiment the architecture of control unit
6 is based on a programmable processing unit which processes
various signals and controls a number of functional modules. A
microprocessor is well suited to perform the computation and
control functions required. Applicator unit 2 is coupled to control
unit 6 by a plurality of signal paths 212, 214, 216, and 218.
Signal path 212 couples display drivers 200, which are controlled
by a computer/controller 236, with indicators 30, 32, 34, and 36 on
the applicator unit. Control button 14 on the applicator unit is
coupled through signal line 214 to an interface 202 and thus to the
computer/controller. Force sensing transducer 42 produces an output
signal indicative of the force (i.e., the pressure) applied against
the surface of the patient's tissues by the applicator unit, and
this signal is conveyed by signal lines 216 to an interface 204,
which provides the signal to the computer/controller. In response
to the magnitude of the monitored force, the computer/controller
produces a control signal applied to a driver 206, which provides
the current signal used to energize force transducer 16, to
determine any additional force that it generates to achieve a
desired pressure on the site of the puncture that is sufficient to
prevent loss of fluid from the vessel, but not so great as to
occlude the flow of fluid through the vessel.
[0079] Signal lines 240 couple ultrasonic array assembly 20 to a
transmit/receive switch 224. The transmit/receive switch determines
the operational mode of the ultrasonic array assembly under the
control of the computer/controller. When operating in a diagnostic
mode in which the ultrasonic array assembly is producing an imaging
ultrasound beam, the signal corresponding to the echo reflected
received by ultrasonic array assembly 20 from tissue and other
structures is conveyed through transmit/receive switch 224 and
through signal lines 222 to an amplifier digitizer array 220. The
output signals from the amplifier digitizer array are conveyed to
computer/controller 236 through signal lines 228. When the
ultrasonic array assembly is generating either the imaging beam or
the HIFU beam, it is responding to signals received from an RF
generator 232 that is coupled to a phase shift/amplifier array 234
by signal lines 236, and to a control signal provided by the
computer/controller and conveyed to the phase shift/amplifier on a
signal line 230. The output of the phase shift/amplifier is
conveyed on signal lines 226 to transmit/receive switch 224, and
thus, to ultrasonic array assembly 20 through signal lines 240.
Manual control inputs 241 are coupled to computer/controller 236
through signal lines 242.
[0080] A number of variously advantageous transducer configurations
may alternatively be employed in this invention. Possibilities
include:
[0081] Configurations wherein therapeutic and, pulse-echo Doppler
functionality are accomplished by the same ultrasonic transducer or
by separate ultrasonic transducers; and,
[0082] Configurations wherein the ultrasonic transducer is either
of a fixed focus type, or a segmented electrically selectable macro
element array, or a phased array, or a linear array, or an annular
array; and,
[0083] Configurations where a large focal spot 412 (see FIG. 13)
(e.g. a focal spot produced by a transducer having an aspheric
shape), or those in which a tightly focused spot is produced;
and,
[0084] Configurations wherein the ultrasonic transducer is
mechanically positioned (or scanned), or those in which it is fixed
in one position.
[0085] An aspheric ultrasonic transducer configuration has the
advantage of covering a large treatment area on the surface of the
vessel without the complication of electronic or mechanical beam
steering. Covering a large area (i.e., overscanning) is desired in
order to ensure that the actual site of the puncture wound is
treated, given its positional ambiguity. FIG. 13 depicts the
geometry of such a configuration. In this embodiment, an ultrasonic
transducer 404, excited by an appropriate RF source via connections
402, is generally aspheric in shape and does not bring the
ultrasound beam to a sharp focus. The ultrasonic energy that it
produces covers area 412 on a vessel 408 that includes puncture
wound 410. Fluid or solid material acoustic coupling (not shown) is
used between the ultrasonic transducer and the tissues of the
patient.
[0086] In one preferred embodiment, the method described includes a
series of manual steps (operator actions) and automated steps. The
automated steps are carried out as control processes or algorithms
executed by one or more processors and other hardware in accord
with machine instructions executed by the one or more processors.
It is understood that variations in the order of these steps, and
in the total complement of steps implemented is possible in
alternative embodiments. Steps as shown in FIG. 4 are described as
follows.
[0087] In a step 100 labeled Patient Preparation, the operator
positions the patient and the apparatus so that the applicator unit
is conveniently positioned over the puncture wound area, e.g., over
the puncture made by a catheter in the femoral artery. Shell 4 is
removed from its sterile package and fitted onto applicator unit 2,
and gel sealing tab 60 (shown in FIGS. 8 and 8A) is removed,
exposing the gel 62.
[0088] A step 102 labeled Manually Align is then carried out. With
the catheter introducer in the wound, the operator palpates the
area locating the point at which the introducer just enters the
artery. The operator marks this location on the patient's skin with
a suitable marking device (e.g. a surgical marker), drawing a line
substantially perpendicular to the perceived direction of the
artery, extending approximately 3 cm from the entry wound location.
It is the purpose of this marking to estimate the longitudinal
location of the wound; the operation of the HIFU sealing process
provides for an overscan of the wound area so that practical
variations in the operator's ability to make the longitudinal
position estimate are permissible. Other techniques for locating
the site of the puncture are discussed below. In a more preferred
embodiment, lateral and range locations of the wound are more
precisely located by the automated capability of the processor(s)
used in the apparatus.
[0089] Also within step 102, the operator places the device over
the wound location, aligning fiducial mark "56" (shown in FIG. 8)
with the line that was drawn on the patient's skin. The applicator
unit is rotated in place until both alignment indicators 12 and 16
(FIGS. 6 and 8) illuminate, indicating that the artery is axially
aligned under the applicator unit.
[0090] The axial alignment indications are, in this preferred
embodiment, derived from two ultrasonic pulsed Doppler
interrogations. FIGS. 10 and 10A show the geometry of the Doppler
alignment beams. Use of a ultrasonic transducer 20 enables the same
ultrasonic transducer to be employed to produce an imaging beam and
the HIFU beam for both a pulse-echo targeting mode and a
therapeutic mode.
[0091] In the alignment sequence illustrated in FIGS. 10 and 10A,
phased array ultrasonic transducer 20 sends and receives a
downstream pulsed Doppler line 304 and an upstream line 308
sequentially. Lines 304 and 308 are in plane with the axial
centerline of the applicator unit and a line perpendicular to the
bottom surface of the applicator unit. Lines 304 and 308 are
transmitted at angles A and B with respect to a line 306, which is
perpendicular to the applicator unit. Angles A and B are chosen to
provide a axial separation as well as an appreciable vector flow
component in the direction of the interrogating line--an angle of
approximately 45 degrees. Direction of flow in an interior 310 of
the vessel is sensed and tested to assure that an artery 300 (not a
vein) is being interrogated. Doppler signals, from lines 304 and
308, integrated over an appropriate range, above a pre-determined
threshold value, are used to cause the illumination of alignment
indicators 12 and 16 respectively. Averaging multiple lines is, in
this preferred embodiment, employed to improve the performance of
the alignment detection scheme. The conditioned signals also set
logical flags so that the system may interlock the initiation of a
therapeutic treatment sequence with assurance of alignment. Thus in
a decision step 106 (FIG. 4), alignment is tested by interrogating
the logical presence of both of the flags.
[0092] Alternatively, another advantageous configuration for
guiding the manual alignment process uses multiple Doppler lines
and multiple indicators, with reference to FIG. 11, which
illustrates a top view of the applicator unit. In this
configuration, three parallel lines are transmitted and received in
the two directions indicated by lines 304 and 308 in FIG. 10.
Additional transducers are appropriately positioned in housing 10
(FIG. 6). Pulsed Doppler signals are processed in a manner similar
to that described above. Thus, for example (referring to FIG. 11),
if the alignment is off-center and rotated to the left, indicator
lights 336 and 334 would be illuminated, indicating the
misalignment and suggesting the appropriate direction to move the
applicator unit to achieve alignment (denoted when indicators 338
and 330 are illuminated). Alternatively, continuous wave Doppler
may be employed to interrogate the flow position of the target
artery, with operation essentially similar to that described
above.
[0093] With verified alignment in step 106, the system proceeds to
a step 108 labeled Set Pressure, wherein the pressure over the
artery is set and controlled within a predetermined range using
force generator 18 (FIG. 6) and force sensing transducer 42. In
this preferred embodiment, the weight of the applicator unit is
purposefully made to be in a range where additional pressure
applied by the operator to hold the unit firmly in place is
reduced. This useful weight is about 1 lb (0.45 kg) or more. Force
generator 18 is activated and controlled such that applied pressure
to the artery partially restricts flow, but maintains sufficient
flow so that thermal cooling due to blood flow within the artery
protects the intimal lining of the vessel from irreversible damage.
Presence of a Doppler flow signal on down-stream line 304 (FIG. 10)
is employed to assure vessel patency.
[0094] In this preferred embodiment, when the system has completed
the pressure application cycle described above, indicator 32 (FIG.
6), which is marked "READY" on the applicator unit is illuminated
(see block 118 FIG. 4), indicating to the operator that a treatment
cycle may be manually initiated (triggered) by pushing control
button 14. The system is in a wait state as indicated in a decision
block 112 in FIG. 4, until a manually triggered treatment cycle is
detected. With the detection of a triggered treatment cycle, axial
alignment is verified in a step 114 by generally repeating the
logical test described at step 102.
[0095] A step 116 then makes a ranging measurement to estimate the
acoustic path length between ultrasonic transducer assembly 20 and
the vessel boundary, i.e., the distance between points F and C
along line 306 in FIG. 10. Pulsed Doppler is, in this preferred
embodiment, employed to make this measurement, wherein lines 304
and 308 measure distances F-D and F-E, respectively. Points D and E
are recognized by the fact that these correspond to the first
instance of flow detected along each line as range increases. The
range estimate of FC is therefore:
FC.about.(FE COS A+FD COS B)/2 Equation 1
[0096] A step 120 estimates the acoustic attenuation at the
therapeutic frequency between ultrasonic transducer assembly 20 and
the target collagen layer overlaying the vascular wound, path F-C
in FIG. 10. In this preferred embodiment, a simplified approach is
employed wherein estimated dimension FC is used to access data in a
look-up table of attenuation values. Attenuation values in the
table are predetermined by empirical measurement. Alternatively,
more sophisticated A-Mode attenuation measurements may be employed
to assess to F-C path.
[0097] A step 122 determines the therapeutic ultrasound exposure
parameters to be employed. Dimension F-C, the attenuation estimate,
and optionally, patient parameters (e.g., size and weight), input
at module 240 in FIG. 9, are used to access predetermined data and
scan protocols in resident look-up tables Ultrasound scan geometry,
intensity and epochal exposure intervals are thus determined.
[0098] Ultrasound scan geometry, intensity and time parameters are
determined to accomplish three key objectives: (1) provide a
sufficient overscan of a longitudinal and lateral surface of the
target vessel so as to include the site of the wound; (2) ensure
delivery of an appropriate energy dose to the collagen layer in the
region of the target site to raise its temperature to a range of
between 60 and 100 degrees Celsius for a predetermined period of
time; and, (3) assure that the skin and interpath tissue is not
exposed to a temperature-time exposure that will result in pain and
or irreversible tissue damage.
[0099] Therapeutic scan geometry is shown in FIGS. 12A and 12B. A
therapeutic level of approximately 50 watts total transmitted
acoustic power, generally weakly focused, is transmitted along a
centerline 314 through a dermal layer 302. The desired scan pattern
is achieved by directing the beam over varying angles of the beam
with respect to a line 320 that extends perpendicular to the center
of the face of the application unit. Thus, for example, a raster
scan pattern may cover a therapeutic area, over collagen layer 318,
of dimensions 1 cm wide by 1.5 cm long (in the arterial axial
direction). Such an overscan of the wound site provides for
variations in the operator's ability to predetermine and locate the
precise lateral position of the wound, as well as the variation in
wound location that results from the possible variation of wound
lateral entry points. Importantly, scan geometry is selected such
that ultrasonic exposure is generally confined to the vessel,
minimizing the possibility that an adjacent vein or nerve structure
will be insonified.
[0100] A step 126 carries out the therapeutic exposure cycle. It is
generally desirable to hold the applicator unit in place, providing
the established orientation and pressure for a period of time after
the therapeutic exposure cycle. A hold interval 130 (FIG. 4) is
selected to enable exposed tissue structures to cool, a time period
of approximately 1 minute. Following this time period, indicator 36
on the application unit (FIG. 6) marked "COMPLETE" is illuminated
and the "HOLD" indicator is turned off, instructing the operator
that the therapeutic treatment is completed and the device may be
removed from the patient.
[0101] In situations where there is concern for inadvertent
exposure of a nerve structure, an additional sequence depicted in
FIG. 4A may optionally be employed. The sequence is inserted into
the process flow of FIG. 4, in this preferred embodiment, at a
location marked "A." To detect the presence of a nerve structure, a
weak, sub-therapeutic energy level ultrasonic pulse is transmitted
in a step 136 (FIG. 4A), to cover the determined target area. The
operator observes in a decision step 138 whether a reaction of pain
and or uncommanded movement from the patient has occurred,
indicating that a nerve structure has been stimulated. System logic
then waits for an addition manually initiated trigger input in
steps 140 and 142, prior to proceeding with therapeutic exposure at
step 126 in FIG. 4.
[0102] Alternative Techniques for Aligning the Applicator Unit
[0103] Step 102, which facilitates alignment of the applicator unit
over the wound area and targeting of the therapeutic exposure, may
be accomplished using several alternative approaches compared to
that described above. It is desired to employ an approach for
targeting and aligning the applicator unit that is easy to
implement and requires minimum operator instruction. The approach
further should be consistent with minimizing bleeding during the
process of achieving alignment. Additionally, the approach should
be robust and provide targeting of the wound site with sufficient
accuracy such that the wound will reliably be included within the
area of therapeutic exposure.
[0104] A principle employed in the present invention is the concept
that the overscan of the target location during therapeutic
exposure is sufficient to accommodate targeting ambiguity and
possible patient or operator movement during the procedure.
Nevertheless, accurate targeting is needed to ensure efficacy of
the wound sealing process.
[0105] In the preferred embodiment described above, pulsed Doppler
ranging was employed to locate the axis of the vessel, and the
operator was advised of the longitudinal location of the wound on
the vessel by reference to visual landmarks on the skin surface.
Alternatively, by inclusion of additional automation, the need for
the operator to locate the longitudinal position is eliminated,
thereby substantially simplifying the targeting procedure for the
operator.
[0106] These alternative approaches make use of the entry channel
along which the introducer and guide wire are commonly passed
during diagnostic and interventional catheterization procedures.
FIG. 5 illustrates the geometry that relates the location of
applicator unit 2 to the locations of an entry channel 518 and a
vessel wound 516. In FIG. 5, applicator unit 2 is positioned on a
patient's skin surface 510 over a vessel 506 in which a blood flow
508 is contained. A location "C" is indicated at wound 516; a line
512 passes from "C" through entry channel 518, intersecting a plane
514 defined by reference locations on applicator unit 2 at a point
"H." A point "F" is a reference point in plane 514. If the spatial
location of line 512 is known relative to plane 514 and point "F,"
and the vector distances "H" to "F", or "C" to "F" are known, then
the location of wound 516 relative to applicator unit 2 is
determinable by basic geometry. Knowledge of this geometry permits
automated system function to be employed to provide guidance
instructions (e.g. visual indicators) to the operator during the
manual alignment portion of the procedure.
[0107] A sufficient number of the parameters in the above described
geometry may be determined by several novel methods and their
associated apparatus. As previously described, acoustic pulsed
Doppler may be employed to determine the distance "C"-"F"
(reference FIG. 5). In many applications of the vascular sealing
method described herein, the vessel is an artery having a
substantial high velocity flow and is thus readily localized using
well known pulsed Doppler techniques. Knowing this distance,
localization of wound 516 on the vessel is made possible by
determining the spatial position of line 512.
[0108] The spatial location of line 512 may be determined by
employing a substantially rigid, straight locator rod 554 as
depicted in FIG. 7, which is placed in entry channel 518. Locator
rod may have a longitudinal center bore 556 through which a guide
wire 552 may pass. In practical use, the introducer used in
conjunction with a clinical procedure would be removed without
removing the guide wire. Locator rod 554 would be introduced into
the wound over the guide wire. Sealing assembly 550 is disposed at
one end of the locator rod to prevent the loss of blood through
center bore 556.
[0109] Several alternative approaches may be employed to determine
the spatial location of the longitudinal axis of locator rod 554
and thus, to determine precise wound location as described above.
These approaches include:
[0110] 1. As shown in FIG. 7A, a spatial position resolving element
558 may be included on locator rod 554. Spatial position resolving
element 558 may be an acoustic position sensor, an optical position
sensor, a magnetic position sensor, an electromechanical
positioning or resolving arm, or an inertial position sensor. The
spatial relationship between the position of locator rod 554 and
applicator unit 2 is accomplished by either a direct mechanical
linkage or by way of an intermediate electronic or computational
circuit.
[0111] 2. As shown in FIG. 7B, an ultrasonic pulse-echo technique
may be employed to determine the spatial location of locator rod
554. A transducer in applicator unit 2 transmits directed acoustic
pulses in more than one direction, e.g., lines 560, 562, and 564,
and echoes from structures in each path are returned and detected
by a pulse-echo receiver included in the applicator unit, as is
well know in the diagnostic ultrasound art. Locator rod 554
provides reflections that permit making time of flight measurements
of, for example, distances "F"-"J," "F"-"K," and "F"-"L." Locator
rod 554 may be coated or constructed of materials chosen to enhance
acoustic reflectivity, thus providing echoes that are readily
distinguished from background clutter. Common guide wires may
alternatively be used as locator rod 554, as these wire structures
are typically highly reflective of ultrasound energy.
Alternatively, locator rod 554 may be constructed from materials
that enhance reflection at a harmonic of the interrogating
ultrasound pulse, providing another advantageous method for clearly
distinguishing the echoes from locator rod 554 from those received
from surrounding tissue. Materials or coatings that entrap gas
bubbles are, for example, effective in providing higher harmonic
reflection. Echo enhancing properties may also be incorporated into
an introducer that is then used as the locator rod. Pulsed Doppler
may also be employed to identify and locate the locator rod. In
this latter alternative, the locator rod may be a common
introducer. A strong Doppler shifted reflection will return from
the lumen of the introducer even when blood is not permitted to
flow out of the introducer.
[0112] 3. As indicated in FIG. 7C, two dimensional, or three
dimensional, imaging may also be employed to locate locator rod
554, the guide wire, and the introducer, as well as the vessel.
FIG. 7C depicts a view of a framed two-dimensional image 580 of the
target region generally orthogonal to that shown in FIGS. 7A and
7B. Distance from the ultrasound source increases toward the bottom
of this depiction. This image is generally representative of a
cross-sectional plane of interrogation located at a line 562 in
FIG. 7B. Automated image recognition provided by the processor may
be employed to identify structures including locator rod 554,
imaged as a locator rod structure 586 and vessel 506, imaged as a
vessel structure 584 in this image. Doppler imaging and color flow
mapping may be employed to increase the recognizablility of
relevant features. The interrogating image plane may be scanned
over the region containing the target. When locator rod structure
586 is recognized at a location just touching the top surface of
vessel structure 584, the wound target site has been
identified.
[0113] Although the present invention has been described in
connection with the preferred form of practicing it, those of
ordinary skill in the art will understand that many modifications
can be made thereto within the scope of the claims that follow.
Accordingly, it is not intended that the scope of the invention in
any way be limited by the above description, but instead be
determined entirely by reference to the claims that follow.
* * * * *