U.S. patent application number 12/012186 was filed with the patent office on 2008-07-10 for systems and methods for delivering ultrasound energy.
This patent application is currently assigned to Timi 3 Systems, Inc.. Invention is credited to Michael J. Horzewski, Veijo T. Suorsa, Todd A. Thompson.
Application Number | 20080167556 12/012186 |
Document ID | / |
Family ID | 46280919 |
Filed Date | 2008-07-10 |
United States Patent
Application |
20080167556 |
Kind Code |
A1 |
Thompson; Todd A. ; et
al. |
July 10, 2008 |
Systems and methods for delivering ultrasound energy
Abstract
Systems and methods deliver ultrasound energy to an ultrasound
transducer having an impedance subject to variations. The systems
and methods electrically couple an ultrasound generator to the
ultrasound transducer to deliver ultrasound energy.
Inventors: |
Thompson; Todd A.; (San
Jose, CA) ; Suorsa; Veijo T.; (Sunnyvale, CA)
; Horzewski; Michael J.; (San Jose, CA) |
Correspondence
Address: |
Daniel D. Ryan;RYAN KROMHOLZ & MANION, S.C.
Post Office Box 26618
Milwaukee
WI
53226-0618
US
|
Assignee: |
Timi 3 Systems, Inc.
|
Family ID: |
46280919 |
Appl. No.: |
12/012186 |
Filed: |
January 31, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10202446 |
Jul 24, 2002 |
7335169 |
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12012186 |
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09935908 |
Aug 23, 2001 |
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10202446 |
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09645662 |
Aug 24, 2000 |
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09935908 |
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Current U.S.
Class: |
600/439 |
Current CPC
Class: |
A61B 90/50 20160201;
A61B 2018/00023 20130101; A61N 7/00 20130101; A61B 2017/00725
20130101; A61B 2017/00734 20130101; A61N 2007/0073 20130101 |
Class at
Publication: |
600/439 |
International
Class: |
A61N 7/00 20060101
A61N007/00 |
Claims
1. A system comprising an ultrasound transducer, an ultrasound
generator coupled to the ultrasound transducer for operation, a use
register sized and configured to be carried by the ultrasound
transducer, the use register comprising a memory field that
registers, according to preprogrammed rules, a prescribed copyright
notice, and a use monitoring controller sized and configured to be
carried by the ultrasound generator and to be coupled to the use
register to control delivery of ultrasound energy through the
ultrasound transducer according to the preprogrammed rules
comprising a preprogrammed rule that compares the prescribed
copyright notice in the memory field to a prescribed content and
disables use of the ultrasound transducer if the prescribed content
is not present in the memory field.
2. A system according to claim 1 wherein the ultrasound transducer
is sized and configured to transcutaneously apply ultrasound energy
to the thoracic cavity.
3. A system according to claim 1 wherein the ultrasound generator
applies to the ultrasound transducer a power density not exceeding
3 watts/cm2 at a maximum total power output of no greater than 200
watts operating at a fundamental therapeutic frequency not
exceeding 500 kHz, whereby the application of ultrasound energy
increases the blood flow of the individual.
4. A system according to claim 1 further including a strap assembly
to stabilize the ultrasound transducer on a chest during
application of ultrasound energy.
5. A method comprising providing an ultrasound transducer providing
an ultrasound generator coupling a use register to the ultrasound
transducer comprising a memory field that registers, according to
preprogrammed rules, a prescribed copyright notice, and coupling a
use monitoring controller to the ultrasound generator to control
delivery of ultrasound energy through the ultrasound transducer
according to a preprogrammed rule that compares the prescribed
copyright notice in the first memory field to a prescribed content
and disables use of the ultrasound transducer if the prescribed
content is not present in the memory field.
6. A method according to claim 5 wherein the ultrasound energy
delivered to the ultrasound transducer is transcutaneously applied
to a targeted tissue region.
Description
RELATED APPLICATION
[0001] This application is a divisional of co-pending U.S. patent
application Ser. No. 10/202,446, filed Jul. 24, 2002 and entitled
"Systems and Methods for Delivering Ultrasound Energy at an Output
Power Level That Remains Essentially Constant Despite Variations in
Transducer Impedance," which is a continuation-in-part of U.S.
patent application Ser. No. 09/935,908, filed Aug. 23, 2001, which
is a continuation-in-part of U.S. patent application Ser. No.
09/645,662, filed Aug. 24, 2000, and entitled "Systems and Methods
for Enhancing Blood Perfusion Using Ultrasound Energy," which are
all incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates to systems and methods for increasing
blood perfusion, e.g., in the treatment of myocardial infarction,
strokes, and vascular diseases.
BACKGROUND OF THE INVENTION
[0003] High frequency (5 MHz to 7 MHz) ultrasound has been widely
used for diagnostic purposes. Potential therapeutic uses for
ultrasound have also been more recently suggested. For example, it
has been suggested that high power, lower frequency ultrasound can
be focused upon a blood clot to cause it to break apart and
dissolve. The interaction between lower frequency ultrasound in the
presence of a thrombolytic agent has also been observed to assist
in the breakdown or dissolution of thrombi. The effects of
ultrasound upon enhanced blood perfusion have also been
observed.
[0004] While the therapeutic potential of these uses for ultrasound
has been recognized, their clinical promise has yet to be fully
realized. Treatment modalities that can apply ultrasound in a
therapeutic way are designed with the premise that they will be
operated by trained medical personnel in a conventional fixed-site
medical setting. They assume the presence of trained medical
personnel in a non-mobile environment, where electrical service is
always available. Still, people typically experience the effects of
impaired blood perfusion suddenly in public and private settings.
These people in need must be transported from the public or private
settings to the fixed-site medical facility before ultrasonic
treatment modalities can begin. Treatment time (which is often
critical in the early stages of impaired blood perfusion) is lost
as transportation occurs. Even within the fixed-site medical
facility, people undergoing treatment need to be moved from one
care unit to another. Ultrasonic treatment modalities must be
suspended while the person is moved.
SUMMARY OF THE INVENTION
[0005] The invention provides systems and methods comprising an
ultrasound transducer and an ultrasound generator coupled to the
ultrasound transducer for operation. The systems and method include
a use register sized and configured to be carried by the ultrasound
transducer. The use register comprises a memory field that
registers, according to preprogrammed rules, a prescribed copyright
notice. The systems and method include a use monitoring controller
sized and configured to be carried by the ultrasound generator and
to be coupled to the use register to control delivery of ultrasound
energy through the ultrasound transducer according to the
preprogrammed rules comprising a preprogrammed rule that compares
the prescribed copyright notice in the memory field to a prescribed
content and disables use of the ultrasound transducer if the
prescribed content is not present in the memory field.
[0006] In one embodiment, the ultrasound transducer is sized and
configured to transcutaneously apply ultrasound energy to the
thoracic cavity.
[0007] In one embodiment, the ultrasound generator applies to the
ultrasound transducer a power density not exceeding 3 watts/cm2 at
a maximum total power output of no greater than 200 watts operating
at a fundamental therapeutic frequency not exceeding 500 kHz,
whereby the application of ultrasound energy increases the blood
flow of the individual.
[0008] In one embodiment, the systems and methods further include a
strap assembly to stabilize the ultrasound transducer on a chest
during application of ultrasound energy.
[0009] Other features and advantages of the inventions are set
forth in the following specification and attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of a system for
transcutaneously applying ultrasound energy to affect increased
blood perfusion.
[0011] FIG. 2 is an enlarged exploded perspective view of an
ultrasound applicator that forms a part of the system shown in FIG.
1.
[0012] FIG. 3 is an enlarged assembled perspective view of the
ultrasound applicator shown in FIG. 2.
[0013] FIG. 4 is a side section view of the acoustic contact area
of the ultrasound applicator shown in FIG. 2.
[0014] FIG. 5 is a view of the applicator shown in FIG. 2 held by a
stabilization assembly in a secure position overlaying the sternum
of a patient, to transcutaneously direct ultrasonic energy, e.g.,
toward the vasculature of the heart.
[0015] FIG. 6 is a side elevation view, with portions broken away
and in section, of an acoustic stack that can be incorporated into
the applicator shown in FIG. 2.
[0016] FIG. 7 is a side elevation view, with portions broken away
and in section, of an acoustic stack that can be incorporated into
the applicator shown in FIG. 2.
[0017] FIG. 8a to 8c graphically depict the technical features of a
frequency tuning function that the system shown in FIG. 1 can
incorporate.
[0018] FIG. 9 graphically depicts the technical features of a power
ramping function that the system shown in FIG. 1 can
incorporate.
[0019] FIG. 10 is a schematic view of a controller that the system
shown in FIG. 1 can incorporate, which includes a frequency tuning
function, a power ramping function, an output power control
function, and a use monitoring function.
[0020] FIG. 11 is a diagrammatic view of a use register chip that
forms a part of the use monitoring function shown in FIG. 10.
[0021] FIG. 12 is a diagrammatic flow chart showing the technical
features of the use monitoring function shown in FIG. 10.
[0022] The invention may be embodied in several forms without
departing from its spirit or essential characteristics. The scope
of the invention is defined in the appended claims, rather than in
the specific description preceding them. All embodiments that fall
within the meaning and range of equivalency of the claims are
therefore intended to be embraced by the claims.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The various aspects of the invention will be described in
connection with the therapeutic indication of providing increased
blood perfusion by the transcutaneous application of ultrasonic
energy. That is because the features and advantages of the
invention are well suited to this therapeutic indication. Still, it
should be appreciated that many aspects of the invention can be
applied to achieve other diagnostic or therapeutic objectives as
well.
[0024] Furthermore, in describing the various aspects of the
invention in the context of the illustrated embodiment, the region
targeted for an increase in blood perfusion is the thoracic cavity
(i.e., the space where the heart and lungs are contained). It
should be appreciated, however, that the features of invention have
application in other regions of the body, too, for example, in the
arms, legs, or brain.
I. System for Providing Noninvasive Ultrasound-Assisted Blood
Perfusion
[0025] FIG. 1 schematically shows a compact, portable therapeutic
system 10 that makes it possible to treat a person who needs or who
is likely to need an increase in the flow rate or perfusion of
circulating blood.
[0026] The system 10 includes durable and disposable equipment and
materials necessary to treat the person at a designated treatment
location. In use, the system 10 affects increased blood perfusion
by transcutaneously applying ultrasonic energy.
[0027] As FIG. 1 shows, the system 10 includes at the treatment
location an ultrasound generating machine 16. The system 10 also
includes at the treatment location at least one ultrasound
applicator 18, which is coupled to the machine 16 during use. As
FIG. 5 shows, the system 10 also includes an assembly 12 for use
with the applicator 18 to stabilize the position of the applicator
18 on a patient for hands-free use. In the illustrated embodiment
(see FIG. 5), the applicator 18 is secured against movement on a
person's thorax, overlaying the sternum, to direct ultrasonic
energy toward the vasculature of the heart.
[0028] The location where treatment occurs can vary. It can be a
traditional clinical setting, where support and assistance by one
or more medically trained care givers are immediately available to
the person, such as inside a hospital, e.g., in an emergency room,
catheter lab, operating room, or critical care unit. However, due
to the purposeful design of the system 10, the location need not be
confined to a traditional clinical setting. The location can
comprise a mobile setting, such as an ambulance, helicopter,
airplane, or like vehicle used to convey the person to a hospital
or another clinical treatment center. The location can even
comprise an everyday, public setting, such as on a cruise ship, or
at a sports stadium or airport, or a private setting, such as in a
person's home, where the effects of low blood perfusion can
arise.
[0029] By purposeful design of durable and disposable equipment,
the system 10 can make it possible to initiate treatment of a
reduced blood perfusion incident in a non-clinical, even mobile
location, outside a traditional medical setting. The system thereby
makes effective use of the critical time period before the person
enters a hospital or another traditional medical treatment
center.
[0030] The features and operation of the system 10 will now be
described in greater detail.
[0031] A. The Ultrasound Generator
[0032] FIG. 1 shows a representative embodiment of the ultrasound
generating machine 16. The machine 16 can also be called an
"ultrasound generator." The machine 16 is intended to be a durable
item capable of long term, maintenance free use.
[0033] As shown in FIG. 1, the machine 16 can be variously sized
and shaped to present a lightweight and portable unit, presenting a
compact footprint suited for transport. The machine 16 can be sized
and shaped to be mounted at bedside, or to be placed on a table top
or otherwise occupy a relatively small surface area. This allows
the machine 16 to travel with the patient within an ambulance,
airplane, helicopter, or other transport vehicle where space is at
a premium. This also makes possible the placement of the machine 16
in a non-obtrusive way within a private home setting, such as for
the treatment of chronic angina.
[0034] In the illustrated embodiment, the machine 16 includes a
chassis 22, which, for example, can be made of molded plastic or
metal or both. The chassis 22 houses a module 24 for generating
electric signals. The signals are conveyed to the applicator 18 by
an interconnect 30 to be transformed into ultrasonic energy. A
controller 26, also housed within the chassis 22 (but which could
be external of the chassis 22, if desired), is coupled to the
module 24 to govern the operation of the module 24. Further
desirable technical features of the controller 26 will be described
later.
[0035] The machine 16 also preferably includes an operator
interface 28. Using the interface 28, the operator inputs
information to the controller 26 to affect the operating mode of
the module 24. Through the interface 28, the controller 26 also
outputs status information for viewing by the operator. The
interface 28 can provide a visual readout, printer output, or an
electronic copy of selected information regarding the treatment.
The interface 28 is shown as being carried on the chassis 22, but
it could be located external of the chassis 22 as well.
[0036] The machine 16 includes a power cord 14 for coupling to a
conventional electrical outlet, to provide operating power to the
machine 16. The machine 16 can also include a battery module (not
shown) housed within the chassis 22, which enables use of the
machine 16 in the absence or interruption of electrical service.
The battery module can comprise rechargeable batteries, that can be
built in the chassis 22 or, alternatively, be removed from the
chassis 22 for recharge. Likewise, the battery module (or the
machine 16 itself) can include a built-in or removable battery
recharger. Alternatively, the battery module can comprise
disposable batteries, which can be removed for replacement.
[0037] Power for the machine 16 can also be supplied by an external
battery and/or line power module outside the chassis 22. The
battery and/or line power module is releasably coupled at time of
use to the components within the chassis 22, e.g., via a power
distribution module within the chassis 22.
[0038] The provision of battery power for the machine 16 frees the
machine 16 from the confines surrounding use of conventional
ultrasound equipment, caused by their dependency upon electrical
service. This feature makes it possible for the machine 16 to
provide a treatment modality that continuously "follows the
patient," as the patient is being transported inside a patient
transport vehicle, or as the patient is being shuttled between
different locations within a treatment facility, e.g., from the
emergency room to a holding area within or outside the emergency
room.
[0039] In a representative embodiment, the chassis 22 measures
about 12 inches.times.about 8 inches.times.about 8 inches and
weighs about 9 pounds.
[0040] B. The Ultrasound Applicator
[0041] As shown in FIG. 5, the applicator 18 can also be called the
"patient interface." The applicator 18 comprises the link between
the machine 16 and the treatment site within the thoracic cavity of
the person undergoing treatment. The applicator 18 converts
electrical signals from the machine 16 to ultrasonic energy, and
further directs the ultrasonic energy to the targeted treatment
site.
[0042] Desirably, the applicator 18 is intended to be a disposable
item. At least one applicator 18 is coupled to the machine 16 via
the interconnect 30 at the beginning a treatment session. The
applicator 18 is preferably decoupled from the interconnect 30 (as
FIG. 1 shows) and discarded upon the completing the treatment
session. However, if desired, the applicator 18 can be designed to
accommodate more than a single use.
[0043] As FIGS. 2 and 3 show, the ultrasound applicator 18 includes
a shaped metal or plastic body 38 ergonomically sized to be
comfortably grasped and manipulated in one hand. The body 38 houses
and supports at least one ultrasound transducer 40 (see FIG.
3).
[0044] In the illustrated embodiment, the ultrasound transducer 40
comprises an acoustic stack 20. The acoustic stack 20 comprises a
front mass piece 32, a back mass piece 34, and one or more
piezoelectric elements 36, which are bolted together. The back mass
piece 34 comprises an annular ring of material having relatively
high acoustic impedance, e.g., steel or stainless steel. "Acoustic
impedance" is defined as the product of the density of the material
and the speed of sound.
[0045] The front mass piece 32 comprises a cone-shaped piece of
material having relatively low acoustic impedance, e.g., aluminum
or magnesium. The piezoelectric elements 36 are annular rings made
of piezoelectric material, e.g., PZT. An internally threaded hole
or the like receives a bolt 42 that mechanically biases the
acoustic stack 20. A bolt 42 that can be used for this purpose is
shown in U.S. Pat. No. 2,930,912. The bolt 42 can extend entirely
through the front mass piece 32 or, the bolt 42 can extend through
only a portion of the front mass piece 32 (see FIG. 7).
[0046] In an alternative embodiment (see FIG. 6), the acoustic
stack 20' of a transducer 40' can comprise a single piezoelectric
element 36' sandwiched between front and back mass pieces 32' and
34'. In this arrangement, the back mass piece 34' is electrically
insulated from the front mass piece 32' by, e.g., an insulating
sleeve and washer 44.
[0047] The piezoelectric element(s) 36/36' have electrodes 46 (see
FIG. 2) on major positive and negative flat surfaces. The
electrodes 46 electrically connect the acoustic stack 20 of the
transducer 40 to the electrical signal generating module 24 of the
machine 16. When electrical energy at an appropriate frequency is
applied to the electrodes 46, the piezoelectric elements 36/36'
convert the electrical energy into mechanical (i.e., ultrasonic)
energy in the form of mechanical vibration.
[0048] The mechanical vibration created by the transducer 40/40' is
coupled to a patient through a transducer bladder 48, which rests
on a skin surface. The bladder 48 defines a bladder chamber 50 (see
FIG. 4) between it and the front mass piece 32. The bladder chamber
50 spaces the front mass piece 32 a set distance from the patient's
skin. The bladder chamber 50 accommodates a volume of an acoustic
coupling media liquid, e.g., liquid, gel, oil, or polymer, that is
conductive to ultrasonic energy, to further cushion the contact
between the applicator 18 and the skin. The presence of the
acoustic coupling media also makes the acoustic contact area of the
bladder 48 more conforming to the local skin topography.
[0049] Desirably, an acoustic coupling medium is also applied
between the bladder 48 and the skin surface. The coupling medium
can comprise, e.g., a gel material (such as AQUASONIC.RTM. 100, by
Parker Laboratories, Inc., Fairfield, N.J.). The external material
can possess sticky or tacky properties, to further enhance the
securement of the applicator 18 to the skin.
[0050] In the illustrated embodiment, the bladder 48 and bladder
chamber 50 together form an integrated part of the applicator 18.
Alternatively, the bladder 48 and bladder chamber 50 can be formed
by a separate molded component, e.g., a gel or liquid filled pad,
which is supplied separately. A molded gel filled pad adaptable to
this purpose is the AQUAFLEX.RTM. Ultrasound Gel Pad sold by Parker
Laboratories (Fairfield, N.J.).
[0051] In a representative embodiment, the front mass piece 32 of
the acoustic stack 20 measures about 2 inches in diameter, whereas
the acoustic contact area formed by the bladder 48 measures about 4
inches in diameter. An applicator 18 that presents an acoustic
contact area of larger diameter than the front mass piece 32 of the
transducer 40 makes possible an ergonomic geometry that enables
single-handed manipulation during set-up, even in confined
quarters, and further provides (with the assembly 12) hands-free
stability during use. In a representative embodiment, the
applicator 18 measures about 4 inches in diameter about the bladder
48, about 4 inches in height, and weighs about one pound.
[0052] An O-ring 52 (see FIG. 4) is captured within a groove 54 in
the body 38 of the applicator 18 and a groove 84 on the front mass
piece 32 of the transducer 40. The o-ring 52 seals the bladder
chamber 50 and prevents liquid in the chamber 50 from contacting
the sides of the front mass piece 32. Thus, as FIG. 4 shows, only
the outer surface of the front mass piece 32 is in contact with the
acoustic coupling medium within the chamber 50.
[0053] Desirably, the material of the O-ring 52 is selected to
possess elasticity sufficient to allow the acoustic stack 20 of the
transducer 40 to vibrate freely in a piston-like fashion within the
transducer body 38. Still, the material of the O-ring 52 is
selected to be sturdy enough to prevent the acoustic stack 20,
while vibrating, from popping out of the grooves 54 and 84.
[0054] In a representative embodiment, the O-ring 52 is formed from
nitrile rubber (Buna-N) having a hardness of about 30 Shore A to
about 100 Shore A. Preferably, the O-ring 52 has a hardness of
about 65 Shore A to about 75 Shore A.
[0055] The bladder 48 is stretched across the face of the bladder
chamber 50 and is preferably also locked in place with another
O-ring 56 (see FIG. 4). A membrane ring may also be used to prevent
the O-ring 56 from popping loose. The membrane ring desirably has a
layer or layers of soft material (e.g., foam) for contacting the
skin.
[0056] Localized skin surface heating effects may arise by the
presence of air bubbles trapped between the acoustic contact area
(i.e., the surface of the bladder 48) and the individual's skin. In
the presence of ultrasonic energy, the air bubbles vibrate, and
thereby may cause cavitation and attendant conductive heating
effects at the skin surface. To minimize the collection of air
bubbles along the acoustic contact area, the bladder 48 desirably
presents a flexible, essentially flat radiating surface contour
where it contacts the individual's skin (see FIG. 4), or a
flexible, outwardly bowed or convex radiating surface contour
(i.e., curved away from the front mass piece) where it contacts
with or conducts acoustic energy to the individual's skin. Either a
flexible flat or convex surface contour can "mold" evenly to the
individual's skin topography, to thereby mediate against the
collection and concentration of air bubbles in the contact area
where skin contact occurs.
[0057] To further mediate against cavitation-caused localized skin
surface heating, the interior of the bladder chamber 50 can include
a recessed well region 58 surrounding the front mass piece 32. The
well region 58 is located at a higher gravity position than the
plane of the front mass piece 32. Air bubbles that may form in
fluid located in the bladder chamber 50 are led by gravity to
collect in the well region 58 away from the ultrasonic energy beam
path.
[0058] The front mass piece 32 desirably possesses either a flat
radiating surface (as FIG. 4 shows) or a convex radiating surface
(as FIG. 7 shows). The convex radiation surface directs air bubbles
off the radiating surface. The radiating surface of the front mass
piece may also be coated with a hydrophilic material 60 (see FIG.
4) to prevent air bubbles from sticking.
[0059] The transducer 40 may also include a reflux valve/liquid
inlet port 62.
[0060] The interconnect 30 carries a distal connector 80 (see FIG.
2), designed to easily plug into a mating outlet in the applicator
18. A proximal connector 82 on the interconnect 30 likewise easily
plugs into a mating outlet on the chassis 22 (see FIG. 1), which is
itself coupled to the controller 26. In this way, the applicator 18
can be quickly connected to the machine 16 at time of use, and
likewise quickly disconnected for discard once the treatment
session is over. Other quick-connect coupling mechanisms can be
used. It should also be appreciated that the interconnect 30 can be
hard wired as an integrated component to the applicator 18 with a
proximal quick-connector to plug into the chassis 22, or, vice
versa, the interconnect 30 can be hard wired as an integrated
component to the chassis 22 with a distal quick-connector to plug
into the applicator 18.
[0061] As FIG. 5 shows, the stabilization assembly 12 allows the
operator to temporarily but securely mount the applicator 18
against an exterior skin surface for use. In the illustrated
embodiment, since the treatment site exists in the thoracic cavity,
the attachment assembly 54 is fashioned to secure the applicator 18
on the person's thorax, overlaying the sternum or breastbone, as
FIG. 5 shows.
[0062] The assembly 12 can be variously constructed. As shown in
FIG. 5, the assembly 12 comprises straps 90 that pass through
brackets 92 carried by the applicator 18. The straps 90 encircle
the patient's neck and abdomen.
[0063] Just as the applicator 18 can be quickly coupled to the
machine 16 at time of use, the stabilization assembly 12 also
preferably makes the task of securing and removing the applicator
18 on the patient simple and intuitive. Thus, the stabilization
assembly 12 makes it possible to secure the applicator 18 quickly
and accurately in position on the patient in cramped quarters or
while the person (and the system 10 itself) is in transit.
[0064] Desirably, when used to apply ultrasonic energy
transcutaneously in the thoracic cavity to the heart, the front
mass piece 32 is sized to deliver ultrasonic energy in a desired
range of fundamental frequencies to substantially the entire
targeted region (e.g., the heart). Generally speaking, the
fundamental frequencies of ultrasonic energy suited for
transcutaneous delivery to the heart in the thoracic cavity to
increase blood perfusion can lay in the range of about 500 kHz or
less. Desirably, the fundamental frequencies for this indication
lay in a frequency range of about 20 kHz to about 100 kHz, e.g.,
about 27 kHz.
II. Controlling the Application of Ultrasound Energy
[0065] To achieve the optimal application of ultrasound energy and
the optimal therapeutic effect, the application of ultrasound
energy should desirably incorporate one or more of the following
features: (1) choice, or tuning, of the output frequency, (2) power
ramping, (3) output power control, and (4) pulsed power.
[0066] A. Tuning of Output Frequency
[0067] Depending upon the treatment parameters and outcome desired,
the controller 26 can operate a given transducer 40 at a
fundamental frequency below about 50 kHz, or in a fundamental
frequency range between about 50 kHz and about 1 MHz, or at
fundamental frequencies above 1 MHz.
[0068] A given transducer 40 can be operated in either a pulsed or
a continuous mode, or in a hybrid mode where both pulsed and
continuous operation occurs in a determined or random sequence at
one or more fundamental frequencies.
[0069] The applicator 18 can include multiple transducers 40 (or
multiple applicators 18 can be employed simultaneously for the same
effect), which can be individually conditioned by the controller 26
for operation in either pulsed or continuous mode, or both. For
example, the multiple transducers 40 can all be conditioned by the
controller 26 for pulsed mode operation, either individually or in
overlapping synchrony. Alternatively, the multiple transducers 40
can all be conditioned by the controller 26 for continuous mode
operation, either individually or in overlapping synchrony. Still
alternatively, the multiple transducers 40 can be conditioned by
the controller 26 for both pulsed and continuous mode operation,
either individually or in overlapping synchrony.
[0070] One or more transducers 40 within an array of transducers 40
can also be operated at different fundamental frequencies. For
example, one or more transducers 40 can be operated at about 25
kHz, while another one or more transducers 40 can be operated at
about 100 kHz. More than two different fundamental frequencies can
be used, e.g., about 25 kHz, about 50 kHz, and about 100 kHz.
[0071] Operation at different fundamental frequencies provides
different effects. For example, given the same power level, at
about 25 kHz, more cavitation effects are observed to dominate,
while above 500 kHz, more heating effects are observed to
dominate.
[0072] The controller 26 can trigger the fundamental frequency
output according to time or a physiological event (such as ECG or
respiration).
[0073] A given transducer 40 can be operated at a frequency within
a certain range of frequencies suitable to the transducer 40. The
optimal frequency for a given treatment is dependent on a number of
factors, e.g., the magnitude of the fill volume of the bladder
chamber 50; the characteristics of the acoustic coupling between
the acoustic contact area (i.e., bladder 48) and the patient's
skin; the morphology of the patient (e.g., size, weight, girth)
which affect the transmission of ultrasound energy through the skin
and within the body; the acoustic load impedance seen by the
transducer 40.
[0074] As FIG. 10 shows, the controller 26 desirably includes a
tuning function 64. The tuning function 64 selects an optimal
frequency at the outset of each treatment session, taking into
account at least some of the above-listed factors. In the
illustrated embodiment (see FIGS. 8A to 8C), the tuning function
sweeps the output frequency within a predetermined range of
frequencies (f-start to f-stop). The frequency sweep can be and
desirably is done at an output power level that is lower than the
output power level of treatment (see FIG. 9). The frequency sweep
can also be done in either a pulsed or a continuous mode, or in a
hybrid mode. An optimal frequency of operation is selected based
upon one or more parameters sensed during the sweeping
operation.
[0075] As FIG. 8A shows, the frequency sweep can progress from a
lower frequency (f-start) to a higher frequency (f-stop), or vice
versa. The sweep can proceed on a linear basis (as FIG. 8A also
shows), or it can proceed on a non-linear basis, e.g.,
logarithmically or exponentially or based upon another mathematical
function. The range of the actual frequency sweep may be different
from the range that is used to determine the frequency of
operation. For instance, the frequency span used for the
determination of the frequency of operation may be smaller than the
range of the actual sweep range.
[0076] In one frequency selection approach (see FIGS. 8A and 8C),
while sweeping frequencies, the tuning function 64 adjusts the
output voltage and/or current to maintain a constant output power
level (p-constant). The function 64 also senses changes in
transducer impedance (see FIG. 8B)--Z-min to Z-max--throughout the
frequency sweep. In this approach (see FIG. 8B), the tuning
function 64 selects as the frequency of operation the frequency
(f-tune) where, during the sweep, the minimum magnitude of
transducer impedance (Z-min) is sensed. Typically, this is about
the same as the frequency of maximum output current (I), which in
turn, is about the same as the frequency of minimum output voltage
(V).
[0077] In an alternative frequency selection approach, the tuning
function 64 can select as the frequency of operation the frequency
where, during the sweep, the maximum of real transducer impedance
(Z) occurs, where:
|Z|= {square root over ((R)}.sup.2+X.sup.2) [0078] and where |Z| is
the absolute value of the transducer impedance (Z), which derived
according to the following expression:
[0078] Z=R+iX [0079] where R is the real part, and X is the
imaginary part.
[0080] In another alternative frequency selection approach, while
sweeping the frequencies, the tuning function 64 can maintain a
constant output voltage. In this approach, the tuning function 64
can select as the frequency of operation the frequency where,
during the sweep, the maximum output power occurs. Alternatively,
the tuning function 64 can select as the frequency of operation the
frequency where, during the sweep, the maximum output current
occurs.
[0081] B. Power Ramping
[0082] As before described, the tuning function 64 desirably
operates an output power level lower than the output power level of
treatment. In this arrangement, once the operating frequency has
been selected, the output power level needs to be increased to the
predetermined output level to have the desired therapeutic
effect.
[0083] In the illustrated embodiment (see FIG. 10), the controller
26 includes a ramping function 66. The ramping function 66 (see
FIG. 9) causes a gradual ramp up of the output power level from the
power level at which the tuning function 64 is conducted (e.g., 5
W) to the power level at which treatment occurs (e.g., 25 W). The
gradual ramp up decreases the possibility of unwanted patient
reaction to the ultrasound exposure. Further, a gradual ramp up is
likely to be more comfortable to the patient than a sudden onset of
the full output power.
[0084] In a desired embodiment, the ramping function 66 increases
power at a rate of about 0.01 W/s to about 10 W/s. A particularly
desired ramping rate is between about 0.1 W/s to about 5 W/s. The
ramping function 66 desirably causes the ramp up in a linear
fashion (as FIG. 9 shows). However, the ramping function can employ
non-linear ramping schemes, e.g., logarithmic or according to
another mathematical function.
[0085] C. Output Power Control
[0086] Also depending upon the treatment parameters and outcome
desired, the controller 26 can operate a given transducer 40 at a
prescribed power level, which can remain fixed or can be varied
during the treatment session. The controller 26 can also operate
one or more transducers 40 within an array of transducers 40 (or
when using multiple applicators 18) at different power levels,
which can remain fixed or themselves vary over time.
[0087] The parameters affecting power output take into account the
output of the signal generator module; the physical dimensions and
construction of the applicator; and the physiology of the tissue
region to which ultrasonic energy is being applied.
[0088] During a given treatment session, the transducer impedance
may vary due to a number of reasons, e.g., transducer heating,
changes in acoustic coupling between the transducer and patient,
and/or changes in the transducer bladder fill volume due to
degassing and/or leaks. In the illustrated embodiment (see FIG.
10), the controller 26 includes an output power control function
68. The output power control function 68 holds the output power
constant, despite changes in transducer impedance within a
predetermined range. If the transducer falls out of the
predetermined range, for instance, due to an open or a short
circuit, the controller 26 shutdowns the generator ultrasound
module 24 and desirably sounds an alarm.
[0089] Governed by the output power control function 68, as the
transducer impedance increases, the output voltage is increased to
hold the power output constant. Should the output voltage reach a
preset maximum allowable value, the output power will decrease,
provided the transducer impedance remains within its predetermined
range. As the transducer impedance subsequently drops, the output
power will recover, and the full output power level will be reached
again.
[0090] Governed by the output power control function 68, as the
transducer impedance decreases, the output current is increased to
hold the power output constant. Should the output current reach a
preset maximum allowable value, the output power will decrease
until the impedance increases, again, and will allow full output
power.
[0091] In addition to the described changes in the output voltage
and current to maintain a constant output power level, the output
power control function 68 can vary the frequency of operation
slightly upward or downward to maintain the full output power level
within the allowable current and voltage limits.
[0092] D. Pulsed Power Mode
[0093] The application of ultrasonic energy in a pulsed power mode
can serve to reduce the localized heating effects that can arise
due to operation of the transducer 40.
[0094] During the pulsed power mode, ultrasonic energy is applied
at a desired fundamental frequency or within a desired range of
fundamental frequencies at the prescribed power level or range of
power levels (as described above, to achieve the desired
physiologic effect) in a prescribed duty cycle (DC) (or range of
duty cycles) and a prescribed pulse repetition frequency (PRF) (or
range of pulse repetition frequencies). Desirably, the pulse
repetition frequency (PRF) is between about 20 Hz to about 50 Hz
(i.e, between about 20 pulses a second to about 50 pulses a
second).
[0095] The duty cycle (DC) is equal to the pulse duration (PD)
divided by one over the pulse repetition frequency (PRF). The pulse
duration (PD) is the amount of time for one pulse. The pulse
repetition frequency (PRF) represents the amount of time from the
beginning of one pulse to the beginning of the next pulse. For
example, given a pulse repetition frequency (PRF) of 30 Hz (30
pulses per second) and a duty cycle of 25% yields a pulse duration
(PD) of approximately 8 msec. At these settings, the system outputs
an 8 msec pulse followed by a 25 msec off period 30 times per
second.
[0096] Given a pulse repetition frequency (PRF) selected at 25 Hz
and a desired fundamental frequency of 27 kHz delivered in a power
range of between about 15 to 30 watts, a duty cycle of about 50% or
less meets the desired physiologic objectives in the thoracic
cavity, with less incidence of localized conductive heating effects
compared to a continuous application of the same fundamental
frequency and power levels over a comparable period of time. Given
these operating conditions, the duty cycle desirably lays in a
range of between about 10% and about 35%.
III. Monitoring Use of the Transducer
[0097] To protect patients from the potential adverse consequences
occasioned by multiple use, which include disease transmission, or
material stress and instability, or decreased or unpredictable
performance, the controller 26 desirably includes a use monitoring
function 70 (see FIG. 10) that monitors incidence of use of a given
transducer 40.
[0098] In the illustrated embodiment, the transducer 40 carries a
use register 72 (see FIG. 4). The use register 72 is configured to
record information before, during, and after a given treatment
session. The use register 72 can comprise a solid state micro-chip,
ROM, EEROM, EPROM, or non volatile RAM (NVRAM) carried by the
transducer 40.
[0099] The use register 72 is initially formatted and programmed by
the manufacturer of the system to include memory fields. In the
illustrated embodiment (see FIG. 11), the memory fields of the use
register are of two general types: Write Many Memory Fields 74 and
Write-Once Memory Fields 76. The Write Many Memory Fields 74 record
information that can be changed during use of the transducer 40.
The Write-Once Memory Fields 76 record information that, once
recorded, cannot be altered.
[0100] The specific information recorded by the Memory Fields 74
and 76 can vary. The following table exemplifies typical types of
information that can be recorded in the Write Many Memory Fields
74.
TABLE-US-00001 Size Field Name Description Location (Byte)
Treatment If a transducer has been 0 1 Complete used for a
prescribed maximum treatment time (e.g., 60 minutes), the treatment
complete flag is set to 1 otherwise it is zero. Prescribed This is
the allowable 1-2 2 Maximum usage time of the Treatment transducer.
This is set Time by the manufacturer and (Minutes) determines at
what point the Treatment Complete flag is set to 1. Elapsed
Initialized to zero. 3-4 2 Usage Time This area is then (Minutes)
incremented every minute that the system is transmitting ultrasound
energy. This area keeps track of the amount of time that the
transducer has been used. When this time reaches the Prescribed
Maximum Treatment Time, the Treatment Complete flag is set to 1.
Transducer This is an area that 5-6 2 Frequency could be used to
prescribe the operational frequency of the transducer, rather than
tuning the transducer to an optimal frequency, as above described.
In the latter instance, this area shows the tuned frequency once
the transducer has been tuned. Average The system reads and 7-8 2
Power accumulates the delivered (Watts) power throughout the
procedure. Every minute, the average power number is updated in
this area from the system, at the same time the Elapsed Usage Time
is updated. when the Usage time clock is updated. This means that
the average power reading could be off by a maximum of 59 seconds
if the treatment is stopped before the Treatment Complete flag is
set. This average power can be used as a check to make sure that
the system was running at full power during the procedure.
Applicator Use Register CRC. This 9-10 2 CRC desirably uses the
same CRC algorithm used to protect the controller ROM. Copyright
Desirably, the name of 11-23 11 Notice the manufacturer is recorded
in this area. Other information can be recorded here as well.
[0101] The on/off cycles of ultrasound transmission could affect
the accuracy of the recorded power levels because of the variance
of the power levels due to ramping function 66. For this reason it
may be advantageous to also record the number of on/off cycles of
ultrasound transmission. This will help explain any discrepancies
in the average power reading. It might also allow the
identification of procedural problems with system use.
[0102] Each use register 72 can be assigned a unique serial number
that could be used to track transducers in the field. This number
can be read by the use monitoring function 70 if desired.
[0103] The following table exemplifies typical types of information
that can be recorded in the Write-Once Memory Fields 76.
TABLE-US-00002 Size Field Name Description (Bytes) Start Date Time
Once the system has tuned the transducer and started to transmit
ultrasound, the current date and time are written to this area.
This area is then locked, which prevents the data from ever-being
changed. Tuned Frequency The tuned frequency is written to this
location when the Start Date and Time is set. This prevents this
information from being written over on subsequent tunes (if
necessary).
[0104] As FIG. 12 shows, when a transducer 40 is first coupled to
the machine 16, and prior to enabling the conveyance of ultrasound
energy to the transducer 40, the use monitoring function 70 prompts
the use register 72 to output resident information recorded in the
memory fields.
[0105] The use monitoring function 70 compares the contents of the
Copyright Notice field to a prescribed content. In the illustrated
embodiment, the prescribed content includes information contained
in the Copyright Notice field of the Write Many Memory Fields 74.
The prescribed content therefore includes the name of the
manufacturer, or other indicia uniquely associated with the
manufacture. If the prescribed content is missing, the use
monitoring function 70 does not enable use of the transducer 40,
regardless of the contents of any other memory field. The
transducer 40 is deemed "invalid." In this way, a manufacturer can
assure that only transducers meeting its design and quality control
standards are operated in association with the machine 16.
[0106] If the contents of the Copyright Notice field match, the use
monitoring function 70 compares the digital value residing in the
Treatment Complete field of the Write Many Memory Fields 74 to a
set value that corresponds to a period of no prior use or a prior
use less than the Prescribed Maximum Treatment Time--i.e., in the
illustrated embodiment, a zero value. A different value (i.e., a 1
value) in this field indicates a period of prior use equal to or
greater than the Prescribed Maximum Treatment Time. In this event,
the use monitoring function 70 does not enable use of the
transducer 40. The transducer 40 is deemed "invalid."
[0107] If a value of zero resides in the Treatment Complete field,
the use monitoring function 70 compares the date and time data
residing in the Write-Once Start Date and Time field to the current
date and time established by a Real Time Clock. If the Start Date
and Time is more than a prescribed time before the Real Time (e.g.,
4 hours), the controller does not enable use of the transducer 40.
The transducer 40 is deemed "invalid."
[0108] If the Start Date and Time field is empty, or if it is less
than the prescribed time before the Real Time, the use monitoring
function 70 deems the transducer 40 to be "valid" (providing the
preceding other criteria have been met). The use monitoring
function 70 reports a valid transducer to the controller 26, which
initiates the tuning function 64. If the Start Date and Time field
is empty, once the tuning function 64 is completed, the controller
prompts the use monitoring function 70 to records the current date
and time in the Start Date and Time Field, as well as the selected
operating frequency in the Tuned Frequency field. The controller 26
then proceeds to execute the ramping function 66 and, then, execute
the prescribed treatment protocol.
[0109] If the Start Date and Time field is not empty (indicating a
permitted prior use), once the tuning function 64 is completed, the
controller 26 immediately proceeds with the ramping function 66
and, then, execute the treatment protocol.
[0110] During use of the transducer 49 to accomplish the treatment
protocol, the use monitoring function 70 periodically updates the
Elapsed Usage Time field and Average Power field (along with other
Many Write Memory Fields). Once the Treatment Complete flag is set
to a 1 value (indicating use of the transducer beyond the
Prescribed Maximum Treatment Time), the use monitoring function 70
interrupts the supply of ultrasound energy to the transducer. The
transducer 40 is deemed "invalid" for subsequent use. The use
monitoring function 70 can also generate an output that results in
a visual or audible alarm, informing the operator that the
transducer 40 cannot be used.
[0111] The information recorded in the use register 72 can also be
outputted to monitor use and performance of a given transducer 40.
Other sensors can be used, e.g., a temperature sensor 78 carried on
the front mass piece 32 (see FIG. 4), in association with the use
register.
[0112] As described, the use register 72 allows specific pieces of
information to be recorded before, during and after a treatment is
complete. Information contained in the use register 72 is checked
before allowing use of a given transducer 40. The use register 72
ensures that only a transducer 40 having the desired design and
performance criteria imparted by the manufacturer can be used. In
addition, the use register 72 can be used to "lock out" a
transducer 40 and prevent it from being used in the future. The
only way the transducer 40 could be reused is to replace the use
register 72 itself. However, copying the architecture of the use
register 72 (including the contents of the Copyright Message field
required for validation) itself constitutes a violation of the
manufacturer's copyright in a direct and inescapable way.
[0113] Various features of the invention are set forth in the
following claims.
* * * * *