U.S. patent application number 10/750369 was filed with the patent office on 2005-07-14 for disposable transducer seal.
This patent application is currently assigned to LipoSonix, Inc.. Invention is credited to Darlington, Gregory Paul, Desilets, Charles S., Etchells, Tim, Quistgaard, Jens U..
Application Number | 20050154308 10/750369 |
Document ID | / |
Family ID | 34739097 |
Filed Date | 2005-07-14 |
United States Patent
Application |
20050154308 |
Kind Code |
A1 |
Quistgaard, Jens U. ; et
al. |
July 14, 2005 |
Disposable transducer seal
Abstract
A disposable transducer seal designed to seal an open aperture
of a transducer housing for a therapeutic ultrasound procedure. The
seal has a membrane, a retainer and a mating device for locking in
place with the transducer housing. The membrane is essentially
transparent to ultrasound energy while being stretched taunt about
the retainer.
Inventors: |
Quistgaard, Jens U.;
(Seattle, WA) ; Desilets, Charles S.; (Edmonds,
WA) ; Darlington, Gregory Paul; (Snohomoish, WA)
; Etchells, Tim; (Bothell, WA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
LipoSonix, Inc.
Bothell
WA
|
Family ID: |
34739097 |
Appl. No.: |
10/750369 |
Filed: |
December 30, 2003 |
Current U.S.
Class: |
600/459 |
Current CPC
Class: |
A61B 2017/22045
20130101; A61B 2017/2253 20130101; A61N 2007/0008 20130101; A61B
8/4422 20130101; A61B 8/4438 20130101; A61N 7/02 20130101; A61B
8/4281 20130101 |
Class at
Publication: |
600/459 |
International
Class: |
A61B 008/14 |
Claims
What is claimed is:
1. A disposable transducer seal comprising: a membrane being
substantially transparent to ultrasound energy, said membrane being
non-porous to water and acoustic coupling fluids; a retainer having
a substantially annular configuration for holding said membrane;
and a means for mating said retainer with a transducer housing.
2. The device of claim 1, wherein the membrane is a thermo-formable
polyimide.
3. The device of claim 1, wherein the retainer further comprises an
electronic recognition device.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The subject matter of the present application is related to
that of the following applications each of which is being filed on
the same day as the present application: U.S. Ser. No. ______,
entitled "Medical Device Inline Degasser" (Attorney Docket No.
02356-000500US); U.S. Ser. No. ______, entitled "Articulating Arm
for Medical Procedures" (Attorney Docket No. 02356-000600US); U.S.
Ser. No. ______, entitled "Acoustic Gel with Dopant" (Attorney
Docket No. 02356-000800US); ______, entitled "Position Tracking
Device" (Attorney Docket No. 021356-000900US); ______, entitled
"Ultrasound Therapy with Hood Movement Control" (Attorney Docket
No. 021356-001100US); ______, entitled "Systems and Methods for the
Destruction of Adipose Tissue" (Attorney Docket No.
021356-001200US); ______, entitled "Component Ultrasound
Transducer" (Attorney Docket No. 021356-001300US); the full
disclosure of each of these applications are incorporated herein by
reference.
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED
RESEARCH AND DEVELOPMENT
[0002] NOT APPLICABLE
REFERENCE TO A "SEQUENCE LISTING," A TABLE, OR A COMPUTER PROGRAM
LISTING APPENDIX SUBMITTED ON A COMPACT DISK.
[0003] NOT APPLICABLE
BACKGROUND OF THE INVENTION
[0004] 1. Field of the Invention
[0005] The present invention pertains to a sealing device for
retaining degassed water within an ultrasound transducer
housing.
BRIEF SUMMARY OF THE INVENTION
[0006] 2. Description of the Prior Art
[0007] Ultrasound transducers require a coupling medium to connect
the transducer to a patient in order to prevent the reflection and
refraction of ultrasound waves when those waves cross a border
between densities of two objects. One of the biggest issues in
coupling transducers to a patient either for a diagnostic
ultrasound device, or a therapeutic ultrasound device, is the
presence of air. Coupling agents are used to eliminate large scale
air bubbles between the transducer and the patient. For diagnostic
purposes, mineral oils, hydro-gels and even water can be used to
couple a transducer to a patient. In therapeutic procedures the
coupling agent should be more strictly controlled so that even
minute air bubbles are eliminated.
[0008] In high intensity focused ultrasound (HIFU) procedures the
need to couple the transducer to the patient often includes a means
of cooling the face of the transducer, or cooling a patient's skin,
with a medium that will pass ultrasound energy with little or no
attenuation or adverse effect. Typically this medium is water held
within a transmission cavity with a cap or membrane, and through
which the ultrasound energy passes.
[0009] One major issue with such a system arises from bubble
formation caused by dissolved gasses being drawn out of solution.
These bubbles provide an impedance mismatch to the ultrasound
energy, causing reflections and localized heating, leading to
observed effects such as reduced effectiveness of therapy, the
destruction of the cap or seal, or patient skin burns.
[0010] Atmospheric water for example, contain approximately 8.5 PPM
(parts per million) O.sub.2, and 14.5 PPM N.sub.2 as well as other
dissolved gasses. Using dissolved oxygen (DO) as an indicator (by
partial pressures the relative contents of other gasses, CO.sub.2,
CO, N.sub.2, etc. . . . can be calculated) it is necessary to
reduce the DO to less than 5 PPM in order to reduce the attenuation
effects to a manageable level.
[0011] The common method used by the industry is to prepare the
fluid by passing it through a filtration and de-ionisation process
to remove impurities and particulates that may precipitate out,
contaminate or provide nucleation sites for bubbles. The coupling
fluid is then degassed to some minimum level before introduced into
the system. Typically degassing is performed by bulk cavitation
under a vacuum or boiling at atmospheric or sub atmospheric
pressure and then sealing the degassed fluid in a container.
[0012] In a completely sealed system the dissolved gas content will
remain constant, but as described below the gas content will strive
to meet equilibrium with the partial pressure of the local
atmospheric conditions. During short procedures or low power
ultrasound procedures the re-gas rate is usually slow enough not to
cause problems. In longer procedures and/or at higher powers, the
probability that re-dissolved gas will be drawn into the fluid, and
subsequently interfere with ultrasound transmission, goes up
considerably since it is impossible to prevent gas diffusing
through the system lining, joints and seals without investing in
prohibitively expensive parts and materials.
[0013] The methods by which gasses come out of solution or enter
the cooling system are various, some examples of the more common
range from pressure changes within the cooling system caused by
physical restriction or atmospheric conditions. Local pressure
changes such as rectified diffusion from HIFU or temperature
changes will bring gas out of solution as will displacement of the
partial pressure of one gas by another, or by material leaching.
Other methods by which gas may enter the system include diffusion
through the tubing, seals and structure of the cooling system in
the same way a balloon deflates, trapping micro bubbles within the
surface structure and pockets of the cooling system, chemical
reactions between materials in the cooling system, or as a by
product of bacterial growth within the cooling system.
[0014] Precautions such as using low permeability materials for the
tubing are regularly employed, but even with such precautions, the
re-gas rate can become a major issue. Other methods used to reduce
the effects of re-gassing include the introduction of surfactants
or wetting agents to prevent bubble formation, using larger volumes
of fluids, and the use of hydrophilic and/or hydrophobic polymers
such as Polyvinaylpyyolidone (PVP). Experimental testing has shown
these provide only a short term solution.
[0015] Numerous examples in the prior art show differing solutions
to the problems of dealing with coupling HIFU transducers to a
patient as well as providing an apparatus for degassing a fluid.
However there has been thus far nothing demonstrating the
feasibility or utility of an in line degassing mechanism combined
with a HIFU therapy system during an actual medical procedure or
application. The use of an inline degasser during a procedure
mandates the use of a transducer housing having a cavity where the
cooling/coupling fluid may circulate around the transducer. To
prevent the coupling fluid from escaping the cavity, a seal is
needed.
[0016] The inability of the prior art to maintain a controlled
dissolved gas content in a cooling fluid over a prolonged procedure
acts as a forced limitation to prolonged HIFU therapy.
[0017] Thus there remains a need for a seal capable of retaining a
degassed coupling fluid for use in a HIFU procedure within a cavity
containing a HIFU transducer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] It is an objective of the present invention to provide for a
seal that is both inexpensive to manufacture, and that can be
quickly and easily installed into a transducer housing.
[0019] It is a further object of the invention to make a seal that
is disposable so reuse and sterility issues need not be an
issue.
[0020] These objectives are provided for in a disposable transducer
seal that comprises a membrane that is substantially transparent to
ultrasound energy. The membrane is non-porous to water and acoustic
coupling fluids. A retainer has an annular configuration. There is
also a means to mate the retainer with a transducer housing.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The device of the present invention is a disposable
transducer seal (seal). The seal is designed for use with a system
for the reduction in adipose tissue. The seal comprises a membrane,
a retainer and a means for attaching the seal to a transducer
housing. The transducer housing is shaped similar to an inverted
cup having a gap space for degassed water. The seal is used to
retain the degassed water in the gap space without the water
spilling onto a patient during an ultrasound procedure. The seal is
intended to provide both an air tight seal, and a barrier to
prevent cross contamination of the different fluids on opposite
sides of the membrane.
[0022] The membrane is composed of a compound being essentially or
substantially transparent to ultrasound energy. The membrane may be
composed of naturally occurring materials such as latex rubber, or
a synthetic material like a thin film plastic or rubber.
Thermoforming plastics produce good membranes since the thickness
of the membrane tends to be uniform. Uniformity in the membrane of
the seal reduces scattering of the ultrasound signal during a
procedure. A thermoforming polyimide provides a good example. For
manufacturing considerations and for optimal performance, the
synthetic polyimide is preferred. The membrane may be flexible or
inflexible as long as it is drawn taunt about the retainer. While
the membrane may be inflexible, it is preferred the membrane be a
little flexible so that it can conform to the curves of a patients
body more readily. Some flexibility also allows the membrane to
respond to fluid pressure changes during procedures. This
responsiveness during a procedure helps maintain a constant
pressure environment for the fluid, since the membrane may expand a
little or contract a little due to variations in pressure in the
system. The membrane serves as an acoustic window, so it is
desirable that the membrane is substantially transparent to
ultrasound energy. Smoothness in its surfaces during manufacturing
will help reduce signal scattering or attenuation, thus improving
performance of the membrane. A plastic membrane having desirable
acoustic properties is required, and if that plastic is
thermo-formable it allows for a greater uniform thickness in the
manufacturing of the membrane. Uniform thickness also helps to
reduce signal scattering or other loss of the ultrasound signal
passing through the membrane.
[0023] The retainer may be assembled from any medically approved
material. However since the retainer may be in direct contact with
the patient, it is preferred to be made of a material that is
easily formable (such as an extruded plastic, or moldable plastic)
so that the sealing device may be discarded after a single use. The
membrane is drawn taunt over the retainer, or drawn taunt and the
retainer is placed down about the membrane so that the membrane
remains taunt during a medical procedure.
[0024] The seal has a means for mating with a transducer housing.
The means may be such as the retainer is shaped as an interlocking
ring with the transducer housing having a conforming receiving
aperture. Or the transducer housing may have clips for latching on
to tabs on the retainer. Other means of mating to the transducer
include a magnetic lock, a screw in pin, a temporary adhesive, an
interference fitting male and female part (one being on the
retainer, the corresponding part on the transducer housing).
[0025] The retainer may also include a means for identifying the
sealing device to the transducer housing, or its attached
ultrasound system. The means may be an electronic device such as an
encoded chip or flex circuit, or it may be linked to the mating
means, such that if the mating is not properly done the transducer
housing and corresponding ultrasound system will not recognize the
retainer and therefore remain in a safe mode.
[0026] Either the membrane or the retainer may also have a clear
window. The window is a small gap space designed to correspond to
the location of an optical emitter and photo-optical receiver such
that an acoustic gel having a safety dopant can be detected by the
transducer housing or ultrasound system through the sealing
device.
[0027] Referring now to the drawings, FIG. 1 illustrates several
possible designs. The retainer 592 of the disposable transducer
seal 590 has an annular configuration. The membrane 594 is drawn
tightly around the retainer 592. Regardless of the material
construction of the membrane, it is necessary for the membrane to
be drawn tightly about the retainer and held in place. Thus if the
membrane is a polymer formed into a thin layer, or a softer latex
rubber, the retainer serves to maintain the shape and rigidity of
the membrane during use. If the membrane is a softer material, such
as a latex rubber, then the retainer serves to keep the membrane
taunt. Preferably the membrane has no slack in it, so there is no
play or deformation of the membrane during use. A limited amount of
deformity is desirable so the membrane can flex slightly to be
concave or convex relative to the transducer. However ripples in
the membrane material, folds or even a somewhat flimsy shape to the
membrane may have adverse effects on the transmission of ultrasound
energy during a procedure. The configuration is a circular ring,
square, rectangle or other loop as required to seal a transducer
housing. Thus the annular configuration depends on the aperture of
the transducer housing the seal must mate with. The precise shape
will vary from one transducer housing to another. The shapes shown
are merely illustrative and not to be taken as limiting in any
sense.
[0028] FIG. 2 illustrates a cross section of the sealing device. As
can be seen the membrane is drawn tightly either within the
retainer (FIG. 2A) or across the surface face of the retainer (2B).
Optional elements include the encoder chip 596 illustrated in both
drawings.
[0029] FIG. 3 illustrates the mating of the seal 590 to a
transducer housing 500. The housing is shaped similar to an
inverted cup containing an electronics and motor assembly for
moving and controlling the transducer and any additional electronic
components that may be integrated into the housing. The seal 590 is
placed over an open aperture on the transducer housing. The design
of the transducer housing is such that the transducer is placed
aperture end toward the patient, and the transducer can abut the
skin of the patient. The transducer housing may be used in two
modes. One of those modes involves the use of degassed water
circulating about the transducer within the transducer housing. A
seal is needed in this mode of operation to prevent the degassed
water from leaking out, and to prevent air from leaking in.
[0030] The seal is mated to the transducer housing. The mating
means may be any number of mechanical connections that allow for
the air and water tight seal described above. Once the seal is in
place, the cavity in the transducer housing may be flooded with
degassed water without water escaping. The seal may also have an
electronic or mechanical recognition device such that the
transducer housing will recognize the proper placement of the seal
and move the ultrasound machine from a safe mode to an active mode.
Furthermore an optical window may be placed either in the membrane
or in the retainer so that any kind of optical sensor or safety
device using an optical sensor may still detect the proper safety
material across the seal.
* * * * *