U.S. patent application number 15/441845 was filed with the patent office on 2017-06-15 for devices that cooperate with ultrasound probes for muscoskeletal evaluations and related systems and methods.
The applicant listed for this patent is Clemson University Research Foundation. Invention is credited to Delphine Dean, David Kwartowitz, Fuad Mefleh, Vipul Pai Raikar, Erika Trent.
Application Number | 20170164929 15/441845 |
Document ID | / |
Family ID | 50385840 |
Filed Date | 2017-06-15 |
United States Patent
Application |
20170164929 |
Kind Code |
A1 |
Kwartowitz; David ; et
al. |
June 15, 2017 |
DEVICES THAT COOPERATE WITH ULTRASOUND PROBES FOR MUSCOSKELETAL
EVALUATIONS AND RELATED SYSTEMS AND METHODS
Abstract
Adaptors for ultrasound probes can have an adaptor body can have
an open lower end that allows a distal end of the ultrasound probe
to extend therethrough to contact skin of a patient. The adaptor
can include a plurality of spaced apart resilient members held by
the adaptor body that, in operation, are able to change in length
such that the resilient members translate from a first longer
length to a second shorter length when the probe applies
compressive force to the target tissue.
Inventors: |
Kwartowitz; David;
(Pendleton, SC) ; Trent; Erika; (Myrtle Beach,
SC) ; Mefleh; Fuad; (Westminster, SC) ; Pai
Raikar; Vipul; (Margao, IN) ; Dean; Delphine;
(Central, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Clemson University Research Foundation |
Clemson |
SC |
US |
|
|
Family ID: |
50385840 |
Appl. No.: |
15/441845 |
Filed: |
February 24, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14034756 |
Sep 24, 2013 |
9615815 |
|
|
15441845 |
|
|
|
|
61707312 |
Sep 28, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 8/0875 20130101;
A61B 8/5223 20130101; A61B 6/463 20130101; A61B 8/4209 20130101;
A61B 8/485 20130101; A61B 8/429 20130101 |
International
Class: |
A61B 8/08 20060101
A61B008/08; A61B 8/00 20060101 A61B008/00; A61B 6/00 20060101
A61B006/00 |
Claims
1. A system for providing data for evaluating soft tissue,
comprising: a circuit that (i) obtains force measurements from an
adaptor releasably attached to an ultrasound probe that defines
forces applied by an ultrasound probe to obtain respective
compressed tissue ultrasound images, a force measurement
synchronized with a corresponding ultrasound image; (ii) calculates
stress using the force measurement and a patient-contact surface
area of a distal end of the ultrasound probe; (iii) segments
obtained ultrasound images to identify a change in length between a
baseline length of the target tissue to a length associated with
the compressed target tissue; (iv) calculates strain based on the
baseline length and change in length; and (v) calculates Young's
Modulus using the calculated stress and strain.
2. The system of claim 1, wherein the circuit attaches the force
measurements as metadata with image data of the ultrasound images
for electronic storage in a PACS.
3. The system of claim 1, wherein the circuit is in communication
with a display and provides a color-coded overlay of tissue
stiffness of the target tissue to a display based on the calculated
Modulus.
4. A method of evaluating muscoskeletal tissue, comprising:
manually pressing an ultrasound probe against skin of a patient to
obtain ultrasound images of compressed target tissue, the
ultrasound probe having a distal end with a patient contact surface
having a surface area; obtaining an ultrasound image of the
compressed target tissue; electronically obtaining a force
measurement from an adaptor releasably attached to the ultrasound
probe; electronically calculating stress using the force
measurement and the probe distal end surface area; electronically
segmenting the obtained ultrasound image to identify a change in
length between a baseline length of the target tissue to a length
associated with the compressed target tissue; electronically
calculating strain based on the baseline length and change in
length; electronically calculating Young's Modulus using the
calculated stress and strain; and electronically providing the
calculated Modulus to a display.
5. The method of claim 4, further comprising synchronizing the
force measurement with the corresponding ultrasound image and
attaching the force measurement as metadata with image data of the
ultrasound image for electronic storage in a PACS.
6. The method of claim 4, further comprising generating a
color-coded overlay of tissue stiffness of the target tissue.
7. The method of claim 4, wherein the target tissue is associated
with a rotator cuff of the patient.
8. The method of claim 4, further comprising repeating the steps at
a second point in time and comparing at least one of the calculated
Modulus, stress and/or strain to monitor disease progress.
9. The method of claim 4, wherein the adaptor is attached to an
external distal end portion of the ultrasound probe, and wherein
the adaptor has an open frame body with upper and lower
substantially rigid members, the adaptor frame body holding a
plurality of spaced apart upwardly extending rods, with opposing
end portions thereof attached to the upper and lower substantially
rigid members, at least one coil spring surrounding each rod and
residing between the upper and lower substantially rigid members,
wherein the at least one force sensor comprises an elongate flex
sensor that extends substantially parallel to and adjacent the at
least one coil spring of at least one of the rods, and wherein, in
response to the manually pressing step and before the obtaining
step, the method further comprises translating the lower member
toward the upper member thereby compressing the coil springs toward
the upper member in response to inward compression of the target
tissue by the ultrasound probe.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 14/034,756, filed Sep. 24, 2013, which claims the benefit
of and priority to U.S. Provisional Application Ser. No.
61/707,312, filed Sep. 28, 2012, the contents of which are hereby
incorporated by reference as if recited in full herein.
FIELD OF THE INVENTION
[0002] The present invention relates to ultrasound
elastography.
BACKGROUND
[0003] Rotator cuff disease impacts over 50% of the population over
age 60, with a range of severity from partial thickness through
total rupture. This disease is believed to be degenerative and will
continue to worsen if there is no intervention. It is currently
believed that the transition from type I to type II collagen in the
tendenous tissue may contribute to rotator cuff disease. In current
clinical practice, treatment decisions are frequently made through
subjective assessment of pain and range of motion combined with
qualitative assessment of X-ray or ultrasound images. Treatment of
disease may include physical therapy, surgery, or a combination of
both. Patient history, physical examination, and medical imaging
are used to determine course of treatment. However, currently there
is little objective data upon which to determine disease
progression or injury, which can lead to unnecessary,
inappropriate, painful, and expensive treatments that may or may
not benefit the patient. Indeed, the final determination of the
best course of action is typically at the subjective discretion of
the clinician, and is often based on personal experiences as
opposed to quantitative standards.
[0004] Ultrasound can visualize and assess subsurface tissues while
posing extremely low risk to the patient and practitioner.
Techniques in ultrasound acquisition and post-processing have been
used for the non-invasive determination of tissue mechanical
properties. This combined process has become known as ultrasound
elastography, and has shown much promise in the diagnosis of
disease and disorder. See, e.g., Garra et al., Elastography of
breast lesions: initial clinical results, Radiology 1997;
202:79-86; Whittaker et al., Rehabilitative ultrasound imaging:
understanding the technology and its applications; J Orthop Sports
Phys Ther 2007; 37: 434-49; and Cochlin et al., Elastography in the
detection of prostatic cancer; Clinical Radiology 2002; 57:
1014-20.
[0005] Despite the foregoing, there remains a need for alternate,
cost effective and easy-to-use devices and systems that provide
objective measurements of tissue elasticity and/or stiffness.
SUMMARY OF EMBODIMENTS OF THE INVENTION
[0006] Embodiments of the present invention provide devices,
circuits, and systems that provide calculated measurements of
tissue stiffness using ultrasound images of tissue compression and
synchronized force measurements used to cause the tissue
compression.
[0007] Embodiments of the invention are directed to adaptors for
ultrasound probes. The adaptors include an adaptor body releasably
attachable to an outer portion of an ultrasound probe. The adaptors
also include at least one force transducer configured to obtain a
force measurement of force applied to target tissue by a respective
ultrasound probe.
[0008] The adaptor body can have an open lower end that allows a
distal end of the ultrasound probe to extend therethrough to
contact skin of a patient. The adaptor can include a plurality of
spaced apart resilient members held by the adaptor body that, in
operation, are able to change in length such that the resilient
members translate from a first longer length to a second shorter
length when the probe applies compressive force to the target
tissue.
[0009] The adaptor body can include an open frame body with upper
and lower substantially rigid members. The adaptor body can hold a
plurality of spaced apart translating members between the upper and
lower substantially rigid members. The lower member can be
configured to contact skin of a patient and translate toward the
upper member thereby forcing the translating members toward the
upper member thereby retracting or compressing the translating
members in response to inward compression of the target tissue by
the ultrasound probe.
[0010] The adaptor body can include a case that substantially
encloses at least one side of the probe body. The adaptor body can
hold a plurality of spaced apart translating members that retract
or compress in response to inward compression of the target tissue
by the ultrasound probe.
[0011] The adaptor can include a plurality of translating members
held by the adaptor body. The translating members can reciprocate
in response to manual inward compression and outward release of
compression of the target tissue by the ultrasound probe.
[0012] The probe has a distal end with a skin contacting surface
having a surface area. The at least one force sensor can include at
least one elongate flexible sensor that extends orthogonal to a
plane extending parallel to the distal end surface.
[0013] The adaptor body can have an open lower end that allows the
distal end of the ultrasound probe to extend therethrough to
contact skin of a patient. The adaptor can further include a
plurality of spaced apart resilient members held by the adaptor
body in communication with the at least one force sensor.
[0014] The adaptor can be in combination with a module that is in
communication with the adaptor and the ultrasound probe that can be
configured to generate at least one of: (i) force measurement data
to metadata of ultrasound images; and (ii) generate a color coded
overlay or mask image of tissue stiffness based on stress and
strain data; and (iii) compute stress, strain and Elastic Modulus
for each segmented region of the target tissue.
[0015] The adaptor can be in combination with a module that can be
configured to synchronize an ultrasound image with a force
measurement by the adaptor, calculate a stress using the force
measurement and a surface area of a distal end of the probe,
identify a change in length from a baseline associated with an
initial at rest or uncompressed tissue thickness length of the
target tissue to a compressed tissue length associated with the
applied force of the target tissue and calculate strain and Elastic
Modulus of the target tissue.
[0016] The adaptor can be in communication with a display
configured to display a color coded overlay of tissue stiffness of
the target tissue using force measurement data from the adaptor. A
display can be in communication with the module that shows the
color coded overlay of tissue stiffness.
[0017] The adaptor body can include an open frame body with upper
and lower substantially rigid members. The adaptor body can hold a
plurality of spaced apart upwardly extending rods, with opposing
end portions thereof attached to the upper and lower substantially
rigid members. The adaptor body can also hold at least one coil
spring surrounding each rod and residing between the upper and
lower substantially rigid members. The at least one force sensor
can include an elongate flex sensor that extends substantially
parallel to and adjacent the coil spring(s) of at least one of the
rods. The lower member can be configured to contact skin of a
patient and translate toward the upper member thereby compressing
the coil springs toward the upper member in response to inward
compression of the target tissue by the ultrasound probe.
[0018] Still other embodiments are directed systems for providing
data for evaluating soft tissue. The systems include a circuit that
(i) obtains force measurements from an adaptor releasably attached
to an ultrasound probe that defines forces applied by an ultrasound
probe to obtain respective compressed tissue ultrasound images, a
force measurement synchronized with a corresponding ultrasound
image; (ii) calculates stress using the force measurement and a
probe distal end, patient-contact surface area; (iii) segments
obtained ultrasound images to identify a change in length between a
baseline length of the target tissue to a length associated with
the compressed target tissue; (iv) calculates strain based on the
baseline length and change in length; and (v) calculates Young's
Modulus using the calculated stress and strain.
[0019] The circuit can (electronically) attach the force
measurements as metadata with image data of the ultrasound images
for electronic storage in a PACS.
[0020] The circuit can be in communication with a display and can
provide a color-coded overlay of tissue stiffness of the target
tissue to a display based on the calculated Modulus.
[0021] Other aspects of the invention are directed to methods of
evaluating muscoskeletal tissue. The methods include: (a) manually
pressing an ultrasound probe against skin of a patient to obtain
ultrasound images of compressed target tissue, the ultrasound probe
having a distal end with a patient contact surface having a surface
area; (b) obtaining an ultrasound image of the compressed target
tissue; (c) electronically obtaining a force measurement from an
adaptor releasably attached to the ultrasound probe; (d)
electronically calculating stress using the force measurement and
the probe distal end surface area; (e) electronically segmenting
the obtained ultrasound image to identify a change in length
between a baseline length of the target tissue to a length
associated with the compressed target tissue; (l) electronically
calculating strain based on the baseline length and change in
length; (g) electronically calculating Young's Modulus using the
calculated stress and strain; and (h) electronically providing the
calculated Modulus to a display.
[0022] The method may also include synchronizing the force
measurement with the corresponding ultrasound image and attaching
the force measurement as metadata with image data of the ultrasound
image for electronic storage in a PACS.
[0023] The method can include generating a color-coded overlay of
tissue stiffness of the target tissue.
[0024] The target tissue can be associated with a rotator cuff of
the patient.
[0025] The method can include repeating the steps at a second point
in time and comparing at least one of the calculated Modulus,
stress and/or strain to monitor disease progress.
[0026] Embodiments of the invention can be used for screening youth
or adult athletes or students or monitoring for changes in tissue
stiffness for earlier or more reliable evaluation of tissue status
or change.
[0027] Embodiments of the invention can be used to evaluate tissue
stiffness associated with the rotator cuff to assess a likelihood
of injury or disease and the need or lack of need for surgical
intervention.
[0028] Embodiments of the invention can be used to differentiate
the difference between type I and type II collagen within the
rotator cuff and to be able to assess the impact this difference
may have on tissue injury or disease.
[0029] It is noted that aspects of the invention described with
respect to one embodiment, may be incorporated in a different
embodiment although not specifically described relative thereto.
That is, all embodiments and/or features of any embodiment can be
combined in any way and/or combination. Applicant reserves the
right to change any originally filed claim or file any new claim
accordingly, including the right to be able to amend any originally
filed claim to depend from and/or incorporate any feature of any
other claim although not originally claimed in that manner. These
and other objects and/or aspects of the present invention are
explained in detail in the specification set forth below.
[0030] Other systems and/or methods according to embodiments of the
invention will be or become apparent to one with skill in the art
upon review of the following drawings and detailed description. It
is intended that all such additional systems, methods, and/or
devices be included within this description, be within the scope of
the present invention, and be protected by the accompanying
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The patent or application contains at least one drawing
executed in color. Copies of this patent or patent application
publication with color drawings will be provided by the Office upon
request and payment of the necessary fee.
[0032] Other features of the present invention will be more readily
understood from the following detailed description of exemplary
embodiments thereof when read in conjunction with the accompanying
drawings.
[0033] FIG. 1 is a front perspective view of an exemplary adaptor
for an ultrasound probe according to embodiments of the present
invention.
[0034] FIGS. 2A and 2B are ultrasound images of non-compressed and
compressed tissue, respectively.
[0035] FIG. 3A is a front perspective view of an assembled adaptor
body according to embodiments of the present invention.
[0036] FIG. 3B is a partially exploded view of the adaptor body
shown in FIG. 3A.
[0037] FIG. 3C is a front perspective view of the adaptor body
shown in FIG. 3A illustrating sensors that can be included
according to embodiments of the present invention.
[0038] FIG. 3D is a top perspective view of the adaptor body shown
in FIG. 3C.
[0039] FIG. 3E is a schematic circuit diagram of the sensor circuit
shown in FIG. 3D according to embodiments of the present
invention.
[0040] FIG. 4 is a schematic illustration of an ultrasound
elastography system according to embodiments of the present
invention.
[0041] FIG. 5A is an exploded view of another embodiment of an
exemplary adaptor body according to embodiments of the present
invention.
[0042] FIG. 5B is a front schematic view of the adaptor body shown
in FIG. 5A with exemplary force sensor and translatable members
according to embodiments of the present invention.
[0043] FIGS. 5C-5E are end views of alternate configurations of
adaptor body cases according to embodiments of the present
invention.
[0044] FIGS. 6A and 6B are flow charts of exemplary operations that
can be used to carry out embodiments of the present invention.
[0045] FIG. 7 is a block diagram of a system according to
embodiments of the present invention.
[0046] FIG. 8 is a flow chart of exemplary operation that can be
used to carry out embodiments of the present invention.
[0047] FIG. 9 is a block diagram of a data processing system
according to embodiments of the present invention.
[0048] FIG. 10 is an ultrasound image of tissue associated with a
rotator cuff of a patient.
[0049] FIG. 11 shows the ultrasound image of FIG. 10 with a
prophetic color coded overlay of tissue elasticity/stiffness that
associates color with objective measured/calculated elasticity
values according to embodiments of the present invention.
[0050] FIG. 12 shows side by side ultrasound images of Ecoflex.RTM.
00-30, with the window on the right associated with compressed
material, and with the window on the left showing an arrow
indicating bubbles increasing attenuation of the ultrasound
signal.
[0051] FIG. 13 is a graph of stress (kPa) versus strain that was
used to determine the Young's modulus for PVA-C phantom.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0052] The present invention now is described more fully
hereinafter with reference to the accompanying drawings, in which
embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art.
[0053] Like numbers refer to like elements throughout. In the
figures, the thickness of certain lines, layers, components,
elements or features may be exaggerated for clarity. Broken lines
illustrate optional features or operations unless specified
otherwise. One or more features shown and discussed with respect to
one embodiment may be included in another embodiment even if not
explicitly described or shown with another embodiment.
[0054] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. As
used herein, the term "and/or" includes any and all combinations of
one or more of the associated listed items. As used herein, phrases
such as "between X and Y" and "between about X and Y" should be
interpreted to include X and Y. As used herein, phrases such as
"between about X and Y" mean "between about X and about Y." As used
herein, phrases such as "from about X to Y" mean "from about X to
about Y."
[0055] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the specification and relevant art and
should not be interpreted in an idealized or overly formal sense
unless expressly so defined herein. Well-known functions or
constructions may not be described in detail for brevity and/or
clarity.
[0056] It will be understood that when an element is referred to as
being "on", "attached" to, "connected" to, "coupled" with,
"contacting", etc., another element, it can be directly on,
attached to, connected to, coupled with or contacting the other
element or intervening elements may also be present. In contrast,
when an element is referred to as being, for example, "directly
on", "directly attached" to, "directly connected" to, "directly
coupled" with or "directly contacting" another element, there are
no intervening elements present. It will also be appreciated by
those of skill in the art that references to a structure or feature
that is disposed "adjacent" another feature may have portions that
overlap or underlie the adjacent feature.
[0057] Spatially relative terms, such as "under", "below", "lower",
"over", "upper" and the like, may be used herein for ease of
description to describe one element or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. It
will be understood that the spatially relative terms are intended
to encompass different orientations of the device in use or
operation in addition to the orientation depicted in the figures.
For example, if the device in the figures is inverted, elements
described as "under" or "beneath" other elements or features would
then be oriented "over" the other elements or features. Thus, the
exemplary term "under" can encompass both an orientation of over
and under. The device may be otherwise oriented (rotated 90 degrees
or at other orientations) and the spatially relative descriptors
used herein interpreted accordingly. Similarly, the terms
"upwardly", "downwardly", "vertical", "horizontal" and the like are
used herein for the purpose of explanation only unless specifically
indicated otherwise.
[0058] It will be understood that, although the terms first,
second, etc. may be used herein to describe various elements,
components, regions, layers and/or sections, these elements,
components, regions, layers and/or sections should not be limited
by these terms. These terms are only used to distinguish one
element, component, region, layer or section from another region,
layer or section. Thus, a first element, component, region, layer
or section discussed below could be termed a second element,
component, region, layer or section without departing from the
teachings of the present invention. The sequence of operations (or
steps) is not limited to the order presented in the claims or
figures unless specifically indicated otherwise.
[0059] The term "about" means that the recited number or value can
vary by +/-20%.
[0060] Embodiments of the invention are particularly suitable for
human uses and/or veterinary uses for muscoskeletal evaluations
including stiffness (elasticity) measurements of tendonous or soft
tissues.
[0061] The term "stiffness" is used interchangeably with
"elasticity" as measures of the same mechanical property of
tissue.
[0062] The term "ultrasound systems" is well known and includes any
commercially available system including, but not limited to:
Acuson's Sequoia.RTM. and Aspen.TM. platforms; Philips/ATL's
HDI.RTM. platforms; General Electric's LOGIQ.TM. platforms;
Toshiba's PowerVision.TM. platforms; Hewlett-Packard's Sonos.TM.
platforms; Siemen's Sonoline.RTM. and Elegra.TM. platforms; and the
like. The instant invention does not depend on the specific type of
ultrasound platform used. The term "ultrasound probe" refers to the
part of the ultrasound system device with the transducer/transducer
array that contacts a patient to obtain ultrasound imaging
data.
[0063] The term "color coded" means that a defined tissue stiffness
or tissue stiffness range is associated with a defined color, hue
or opacity of a color so that an image with different colors, hues
or opacities or the same can visually illustrate common and
different stiffness values. The color coded image can be integrated
into an ultrasound image and/or may be provided as an overlay on
the image of the FOV (field of view) tissue. A User Interface (UI)
such as a Graphic User Interface (GUI) can be in communication with
a display circuit and configured to allow a user to selectively
apply the color coding onto the tissue. Where an overlay is used,
the UI may also allow a user to increase the intensity from hidden
to dominant over the ultrasound image.
[0064] Turning now to the figures, FIG. 1 illustrates an assembly
10 with an ultrasound probe 20 and an applied-force measurement
adaptor 30. In some embodiments, the adaptor 30 is releasably
attachable to the probe 20. The adaptor 30 can be configured to
attach to probes 20 in clinical use, e.g., for retrofit of or use
with existing systems 50 (FIG. 4) in various field sites or
clinical sites.
[0065] The adaptor 30 can cooperate with the probe 20 to perform
tissue elastography. The adaptor 30 can measure the force applied
by an ultrasound probe 20 during ultrasound imaging. This adaptor
30 can be instrumented with at least one force transducer 32 (also
interchangeably called a force sensor). The adapter 30 can include
a connector 139 to the sensor 32. From the known dimensions of the
ultrasound probe 20 applying the force, the stress at the tissue
surface can be computed. Typical applied forces are between about
0-6 lb.sub.f such as between about 0.25-5 lb.sub.f.
[0066] The adaptor 30 can also include at least one angular and
acceleration sensor. These sensors can allow for the (typically
electronic) computation of the force applied by the ultrasound
probe 20, resulting joint torsion, and acceleration.
[0067] FIGS. 2A and 2B are examples of a typical ultrasound image
of the rotator cuff showing the humeral head and insertion of the
bicep. The tissue boundaries are clearly visible. FIG. 2A shows no
compression and FIG. 2B shows moderate compression. The tissue
boundaries are visible and the change in tissue thickness due to
the compression can be electronically identified and computed.
[0068] Ultrasound images allow for the visualization of subsurface
tissue boundaries in a real-time sense. These images can be
processed to compute the deformation due to the applied stress.
From the (real-time) tissue deformation with a calculated force,
the tissue strain can be calculated. Using the tissue stress and
strain, the tissue compressive modulus can then be computed and
compared to determine tissue composition. The elasticity of a
material is defined by a quantity known as Young's Modulus (E),
which is a function of stress (.sigma.) and strain (.epsilon.).
Stress is a property of an applied force (F) applied over a surface
area (A), while strain is a change in the length of the material ()
as a function of its original length (.sub.o). This relationship is
shown in Equation 1, in which local elasticity in tissues can be
computed given a known transducer area (A) and the measurement of
the applied force (F) at the distal end of the probe for the
ultrasound transducer. The length and change in length can be
measured from the resulting ultrasound images.
.sigma. = F A = .DELTA. l l o = l - l o l o E = .sigma. = ( F / A )
( l - l o / l o ) = F ( l o ) A ( l - l o ) Eqn . 1
##EQU00001##
[0069] Referring again to FIG. 1, as noted above, the adaptor 30
includes at least one force transducer 32. A respective force
sensor 32 can include any suitable force transducer. In the
embodiment shown, the force sensor 32 includes a flex sensor
32f.
[0070] In some embodiments, the adaptor 30 includes at least one
upstanding translating member 35. The sensor 32 can run parallel to
at least one of the at least one translating member 35. The at
least one translating member 35 can include a resilient member 37.
The sensor 32 can be oriented to run substantially parallel to the
axial direction of the resilient member 37. The sensor 32 can
comprise a flex sensor 32f which can have a length that is at least
a major portion of a length of the translating member 35, e.g., the
resilient member 37, but less than the entire length in an
uncompressed or ready to use configuration.
[0071] The wire connector 139 of the force sensor 32 can reside on
an outer surface of the adaptor body 30b for ease of access. In
other embodiments, the connector 139, where used, can be held
inside the adaptor 30 and wiring access can be via a harness. The
at least one translatable member 35 can be attached (directly or
indirectly) to a lower surface 31 of the adapter 30 to be able to
move away from the tissue and distal end of the probe 20d.
[0072] Other force sensors may be used, including, for example, a
load cell sensor or a linear variable differential transducer
(LVDT) that can be used within a load cell to measure the
displacement of the resilient member 37. However, as is known to
those of skill in the art, other transducers/sensors 32 may be
used, including, for example, piezoelectric transducers. Examples
of a suitable commercially available flex sensor includes the Flex
Sensor FS-L-0055-253-ST, from Spectra Symbol, Salt Lake City,
Utah.
[0073] An alternative embodiment, which may be particularly
suitable for the embodiment shown in FIG. 5A, can employ one or
more load cell sensors, such as the Omega, LCL-005, from Omega
Inc., Stamford, Conn.
[0074] For the calculations described herein, the area (A) of the
probe 20 can be selected based on a reference brochure, website or
manual or electronic look-up table or other chart or data of
different manufacturer probes and associated sizes (area).
[0075] Also in FIG. 1, the adapter 30 is shown as comprising two
laterally spaced apart upstanding translating members 35 that
include respective shafts 36 that reside across from each other on
either side of an open space 30s that holds the probe 20. However,
additional such members 35, e.g., front and back as well as side to
side positions, can be used to help stabilize, distribute or
equalize the translational response of the surface 31 to the probe
applied force, which may be appropriate for providing reliable
measurements in some embodiments.
[0076] In the embodiment shown in FIG. 1, one of the translating
members 35 includes an upstanding member 131 attached to the upper
surface of a patient contacting surface 31 (shown on the left side
of the adaptor 30) that is aligned with a downwardly extending
(static) member 132 residing above the member 131. The lower member
131 moves up in response to downward compression of the probe 20
against a patient and the flex sensor 32f defines the applied
force.
[0077] In other embodiments, a graduated scale can be used with an
optical reader or encoder can define the applied force based on a
correlation of distance between the two members 131, 132 to an
applied force.
[0078] In some embodiments, one translatable member 35 can be the
master and another one or more can be the slave member. The master
translatable member 35 can reside proximate the sensor 32. The
slave member 35 can provide structural stability without providing
any force measurements. In other embodiments, two or more master
translatable members 35 can be used, each with sensors 32 and an
average (or mean) force can be calculated using two or more force
measurements of the applied force.
[0079] In some embodiments, the translatable members 35 can be
attached, directly or indirectly, to a bottom patient contacting
surface 31 that is in communication with a plurality of rods 36.
Each rod 36 can be in communication with at least one resilient
member 37. In operation, the surface 31 presses against external
skin of the patient in response to a user pushing the probe 20
against the patient to compress internal tissue. The adaptor 30
(via the surface 31) then pushes the translatable member(s) 35
linearly away from the patient toward the proximal end of the probe
20p.
[0080] The translatable member(s) 35 can include a resilient
(elastomeric) or other member such as, for example, gas
cylinders/dampers that linear translate a known distance for a
defined applied force.
[0081] FIG. 1 illustrates the translatable members 35 comprise a
lower member 131, rod 36 and resilient member 37 that can be
attached to or reside proximate the lower upwardly facing surface
of the probe adapter 30 as shown. Although as one coil spring for
each rod, more than one coil spring may be used of the same or
different spring factors. Where springs are used, they can
typically have a spring factor "K" in the range of between about
1000 N/M up to about 5000 N/M. In some embodiments, K can be about
1000 N/M, about 2000 N/M, about 3000 N/M, about 4000 N/M or about
5000 N/M or any value therebetween. In some particular embodiments,
K is about 3000 N/M.
[0082] Also, other resilient components and/or translatable member
configurations can be used can be used with or instead of the coil
spring and with or without the rod(s). For example, one or more
leaf springs, (stacked) dome washers, one or more O-rings or
washers, Belleville springs, Clover-Dome spring washers (see, e.g.,
U.S. Pat. No. 6,705,813), or any other type of flexible elastic
member including, for example a solid resiliently deformable
elastic (polymeric) member (polyurethane or other suitable
material). Combinations of different types of elastic or resilient
members and/or more than one of the same type may also be used.
[0083] As shown in FIG. 1, the adaptor 30 can include translatable
members 35 that can face each other across an open medial portion
30p of the adapter, e.g., on opposing sides of the probe 20, and
can, in concert, linearly retract, compress or deform with a
defined stiffness to allow the sensor to generate the applied force
measurement. As will be discussed further below, the translatable
member(s) 35 can have an adjustable stiffness so that the linear
movement for a particular applied force or set of forces varies
according to target tissue or patient (e.g., pediatric versus adult
or athlete and the like).
[0084] In some embodiments, where resilient members 37 are used,
the resilient (elastically deformable) members 37 can be configured
to have a defined k-factor (spring constant) and/or stiffness. The
members 37 can be selected for use with the adaptor 30 based on
different target tissues or patients. Where gas cylinder dampers
(miniature) are used, the actuation stroke associated with the
cylinder/gas can be adjusted for different tissue/patients.
[0085] In some embodiments, the adaptor 30 can be a "universal"
adaptor meaning that it can be assembled to different probes 20
from the same or even different manufacturers. As shown in FIGS. 1,
3A-3D, the adaptor 30 can have a frame 30f with an open frame body
configuration with upper and lower cooperating horizontally
oriented frame members 30u, 30l that trap two laterally spaced
apart rods 36 attached to the frame members inside two resilient
members 37. An open slot 135 in the upper frame 30u cooperates with
a collar 33 (FIG. 1) or other mounting member that can be provided
in different sizes to provide the probe to adaptor interface
adjustability to allow for assembly to different probe bodies using
a common primary adaptor body such as a frame body. In other
embodiments, the adaptor 30 can be configured to attach to a
specific probe configuration. In this embodiment, the adaptor 30
has a frame 30f with an open frame body that allows visual access
to the probe 20. FIG. 3B illustrates that the upper frame member
30u can include two closely spaced cooperating members that hold
the probe proximal or upper end. Open center spaces 30p can be
aligned with the top frame member having a smaller opening relative
to the underlying upper frame member 30u.sub.1, 30u.sub.2,
respectively. FIGS. 3A and 3B are shown in a partial assembly
configuration without the sensors and it is also noted that the
lower threaded portions of the rods typically do not extend outside
the lower frame surface (or at least do not contact the patient)
for patient comfort.
[0086] FIGS. 3C and 3D illustrate the adaptor 30 with two flex
sensors 32f. FIGS. 3C and 3D also illustrate a circuit board 300c
(which can be a rigid or substantially rigid printed circuit board
or a flex circuit) with three sensors thereon, including an
accelerometer 133, a magnetometer 134 and a gyroscope 136. FIG. 3E
illustrates an exemplary circuit schematic of the circuit 300c.
[0087] The adaptor 30 may also include an angulation and
accelerometer sensor. The adaptor 30 can be battery powered, may be
AC powered into a power source or may be powered by connecting to a
port of a portable device, e.g., smart phone or notebook.
[0088] FIG. 5A illustrates that the adaptor 30 can have a body 30b
that can be more form-fitting, e.g., having a shape substantially
similar to the body of the probe 20 and may have upstanding walls
30w that encase a respective probe 20 while leaving the distal end
30d open and free to contact a patient. The adaptor 30 can have a
substantially closed shell or case body with matably attachable
front and back components 30c as shown in FIG. 5A. The adaptor 30
may also have a body that substantially encloses the probe body but
may have an external shape that is different than the probe 20.
[0089] FIG. 5B illustrates that the internal wall 30i of the shell
or case 30c can hold the translatable member 35 of the force sensor
32, shown as comprising resilient members 37 held in place with
rods 36. The rods 36 can slidably move up and down relative to the
upper ledge, e.g., through a slot or hole. The rods 36 can have
feet that can form part of a patient contacting surface 31 used to
define linear movement for measuring applied force.
[0090] FIGS. 1, 5B, 5C, 5D and 5E also illustrate that the adaptor
30 can have a patient contacting surface 31 that abuts against skin
of the patient and translates in an opposing direction away from
the compression direction of the probe 20 as the probe 20 pushes
inward/down to compress target tissue being imaged. The patient
contacting surface 31 can be defined by a substantially rigid
portion of the probe body. The patient contacting surface 31 can be
annular and surround the probe 20 as shown in FIG. 1. FIGS. 5A and
5B illustrate that the surface 31 is not required to surround the
probe 20. This surface 31 may be discontinuous about the probe
perimeter.
[0091] FIGS. 5C and 5D illustrate different exemplary embodiments
of the patient-contacting surface 31 of the adaptor 30 for the
force sensor 32. FIG. 5C illustrates the patient contacting
surfaces 31 on the opposing long sides of the adaptor 30 while FIG.
5D illustrates the patient contacting surfaces 31 on the adaptor
short sides. The surfaces 31 can also reside on all sides. The term
"sides" does not require the perimeter to have a rectangular shape
as other geometric shapes may be used.
[0092] FIG. 5E illustrates that the adaptor body 30b can partially
enclose the probe body 20 to leave an open long space 30s on one
side for ease of assembly. A cover plate may be attached to the
open space 30s of the body 30b or this space 30s can remain open
during use. In other embodiments, the adaptor body 30b only
includes one of the shell or case components 30c shown in FIG. 5A,
leaving the probe open on one side.
[0093] As shown in FIGS. 1, 5B, 5C, 5D and 5E, the adaptor 30 is
configured to define an open bottom that allows the probe 20 to
directly contact the patient's skin.
[0094] The surface 31 can be substantially flat and may have
ridges, ribs, embossment features or grip regions. Typically, the
surface 31 has a symmetric shape and is sufficiently large to
provide adequate support for allowing the surface to push in an
opposing direction from the probe 20 for a transducer to generate
the applied force measurement. The surface 31 can have a width that
is between about 0.1 inches to about 0.5 inches in some
embodiments. The surface 31 can have a constant width about its
perimeter or the width may vary over its perimeter.
[0095] As noted above, different adaptors 30 can be provided with
predefined/known different stiffness for the defined linear
movement to force relationship. In some embodiments, translatable
members 35 and/or the members 37 themselves can be interchanged on
a respective adaptor 30 to use those from a kit of defined
resilient members.
[0096] FIGS. 1 and 3A illustrate different coil springs 37c (one
has a different stiffness than the other) that may be used with the
same adaptor 30. Different rated members 35 can be color coded or
marked by rating for a user's ease in selecting for concurrent use
on a respective device 30, for ease of identification. The
translatable members 35, e.g., springs or other resilient members
37, can include electronically readable media, e.g., barcodes,
linear or 2-D (e.g., QR) barcodes or that can be read by the
ultrasound system 50 (FIG. 4), and/or a portable computer (e.g.,
electronic notebook or smart phone), or an electronic reader
onboard or in communication with the adaptor 30 to confirm or
identify a part number, type or rating of member 35 that is
on-board the device 30 and to optionally confirm that each
translatable member station/position has a the same stiffness-rated
resilient member (or activation can be locked out, an audible or
visual alert can be generated or an error may be displayed on a
display). Alternately, a user can enter the type and/or stiffness
rating of member 35 for use.
[0097] FIG. 4 illustrates an exemplary ultrasound system 50 that is
in communication with the probe 20 and includes or is in
communication with a tissue stiffness calculation module 100 that
uses data from the applied-force measurement adaptor 30 and
compression measurements from an ultrasound images taken of
compressed tissue. The compressed tissue image is synchronized with
a corresponding applied force measurement so that the force used to
cause the change in tissue thickness in the compressed tissue is
defined. The adaptor 30 can connect to an input port 56 on the
ultrasound system (e.g., a USB or other defined port). In some
embodiments the adaptor 30 can connect to a separate device 125
such as a remote device instead or in addition to the ultrasound
device 50.
[0098] The module 100 can reside partially or totally on-board the
ultrasound system 50 (e.g., in the computer and/or processor
thereof) or can reside partially or totally remotely in one or more
remote processors. The module 100 can reside on the separate device
125 which can be a portable electronic device such as a laptop,
smart phone (e.g., IPHONE.TM.), notebook or other pervasive
computing device that wirelessly or in a wired manner communicates
with the adaptor 30 and/or ultrasound system 50 for access to the
ultrasound compressed image data (e.g., an ultrasound image module)
and the applied force data from the adaptor 30. The module 100 can
partially or totally reside in a server such as in a PICTURE
ARCHIVING AND COMMUNICATION SYSTEM ("PACS") system. The module 100
can be configured to transmit images and overlays to a server such
as a PACS server and may record or match force measurements in
image metadata. PACS is a system that receives images from imaging
modalities, stores the data in archives, and distributes the data
to clinicians for viewing (and can refer to sub portions of these
systems).
[0099] The term "module" is used interchangeably with "circuit" and
refers to an entirely software embodiment or an embodiment
combining software and hardware. The module or modules can reside
in one or more signal processors that include or communicate with
electronic memory. The processor(s) can be any commercially
available or custom microprocessor. The memory is representative of
the overall hierarchy of memory devices containing the software and
data used to implement the functionality of the data processing
system. The memory can include, but is not limited to, the
following types of devices: cache, ROM, PROM, EPROM, EEPROM, flash
memory, SRAM, and DRAM.
[0100] As noted above, the circuit or module 100 can synchronize a
force measurement from the adaptor 30 with the corresponding
compressed ultrasound image. The module 100 can reside on the
ultrasound system 50, in the separate device 125 which can be a
mobile device (such as in an APP on that device), on-board the
adaptor 30, in a PACS or hospital database or one or more remote
servers 150. The one or more servers 150 can be provided using
cloud computing which includes the provision of computational
resources on demand via a computer network. The resources can be
embodied as various infrastructure services (e.g. computer,
storage, etc.) as well as applications, databases, file services,
email, etc. In the traditional model of computing, both data and
software are typically fully contained on the user's computer; in
cloud computing, the user's computer may contain little software or
data (perhaps an operating system and/or web browser), and may
serve as little more than a display terminal for processes
occurring on a network of external computers. A cloud computing
service (or an aggregation of multiple cloud resources) may be
generally referred to as the "Cloud". Cloud storage may include a
model of networked computer data storage where data is stored on
multiple virtual servers, rather than being hosted on one or more
dedicated servers. Data transfer can be encrypted and can be done
via the Internet using any appropriate firewalls to comply with
industry or regulatory standards such as HIPAA. The term "HIPAA"
refers to the United States laws defined by the Health Insurance
Portability and Accountability Act. The patient data can include an
accession number or identifier, gender, age and force measurement
data as meta data for the ultrasound images.
[0101] FIG. 6A is a flow chart of exemplary preliminary operations
that can be used to calculate tissue thickness before compression
of tissue (e.g., when the applied force is "0") which may be
carried out prior to activation of the adaptor 30. One or more
ultrasound images can be obtained (block 200) and electronically
segmented (block 210). Tissue thickness can be computed (block 220)
and provided as a parameter of "tissue thickness 1" (block 225).
The adaptor 30 with the force transducer can be activated (block
250). The force measurement is used to calculate stress (block 255)
based on a known value of surface area of the probe in use. If the
force is "0", the initial tissue thickness can be defined for this
"at rest" or pre-compression evaluation to define an initial tissue
thickness (block 265). This thickness can be defined as the
original length (.sub.o). Where the steps of FIG. 6A have also been
performed, the two values of initial thickness (.sub.o) may be
compared the value from block 225 and the value from block 265. If
there is a difference, an alert may be generated or if within a
defined tolerance an average measurement can be used. Steps 250-260
may be omitted where steps 200-225 were previously carried out. In
any event, the system may generate an error alert if the initial
extent has not been computed (block 266). Of course, the initial
extent can also be calculated after the compressed extent is
calculated. As shown, stress, strain, and Elastic Modulus are
calculated/computed for each segmented region of interest (for
moving joints, potentially at different angles) (block 270). A mask
or color-coded overlay image or color-coded image itself of stress
and strain data (e.g., Modulus) can be created (block 275). The
overlays of the stress/strain data can be displayed (block 280).
The ultrasound images and associated overlays can be sent to a
server (such as a PACS server) and force measurements can be
recoded/appended to image metadata (block 285).
[0102] FIG. 7 is a schematic illustration of a system 100s with a
stiffness (stress/strain) calculation module 100 that is in
communication with a synchronization module 110, a color-coded
tissue stiffness image module 115, an ultrasound image module 60
and a display 55. As shown, the display 55 can be on-board the
ultrasound system 50 but may also be associated with a different
device or both the on-board display and a different display. The
system 100s can communicate with a PACS or other server 150.
[0103] The system 100s may include or be in communication with an
electronic library or database 117 of population norms or
standards/ranges that allow a clinician to compare normal or
abnormal measurements of tissue stiffness for different defined
tissues and the population norms/standards can be further segmented
or grouped by/age, gender and ethnicity. Embodiments of the
invention can generate an audio or visual alert when abnormal
measurements for a target tissue are calculated and/or when
measurements taken over time indicate an increase in the risk of
injury or disease progression.
[0104] Because of the degenerative nature of rotator cuff disease,
early diagnosis may be key to preventing disease progression. A
quantitative assessment of tissue material properties may be able
to be used as a predictive screening test or be used to properly
stage patients for treatment, which may be particularly suitable
for rotator cuff disease, which has a high incidence, with a high
societal cost. This incidence is correlated with age, and as the
population ages, the cost of this disease will only increase. Thus,
the use of ultrasound elastography may predict the occurrence of
rotator cuff disease, thus allowing for early diagnosis treatment.
Through this early diagnosis, there may be a net reduction in the
necessary treatment, and thus total cost of this common and
debilitating disease.
[0105] FIG. 8 is a flow chart of operations that can be used to
carry out embodiments of the present invention. The ultrasound
probe is manually pressed against skin to compress target tissue
(block 290). A force measurement is synchronized with the
ultrasound image obtained using the associated force that provides
the tissue compression in that image (block 295). A color-coded
tissue map can be generated and overlayed or applied to ultrasound
image data of tendonous patient tissue (block 300).
[0106] The adaptor can be releasably attached to the probe (block
291). A software application (APP) can be downloaded or the
software module can otherwise be loaded onto one or more processors
to provide a tissue stiffness calculation functionality (block
292). Control software on a portable device with a processor can be
connected to a USB port on the ultrasound system and/or the adaptor
can be connected to the portable device and/or. USB port on the
ultrasound system (block 294).
[0107] A manual depression of a trigger on or associated with the
ultrasound probe used to obtain the image can be used to
synchronize the force measurement to correlate to the appropriate
image and may include a time stamp (block 296).
[0108] The adaptor 30 can be portable and may universally fit to
existing ultrasound probes of commercially available systems. The
adaptor 30 can include an onboard display or transmit data to the
ultrasound display so that the applied force value of an associated
image can be substantially continually displayed (and may be
displayed with off and on GUI user selection). The systems can
provide synchronization between force, imaging, and positional data
of the patient. Using force and image data, the local tissue
elasticity (or stiffness) can be computed. Image overlays can be
made to show local elasticity. Based on the elasticity data, a
database of patient data for future diagnostic evaluations/tools
can be generated. The tissue elasticity measurements can
objectively assess tissue and quality of images.
[0109] The devices and systems can be used to evaluate or screen
athletes, particularly young (college age and younger) athletes.
Due to repeated motion and traumatic injury, athletes may have
tears at younger ages. The device is non-invasive and poses no
patient risk and can act as screening test before clinical injury
is reached. Embodiments of the invention can provide a technology
to improve tendon pathology diagnosis, reduce unnecessary and
costly treatments, and unnecessary surgical intervention.
[0110] FIG. 9 is a block diagram of exemplary embodiments of data
processing systems 405 that illustrates modules, circuits, systems,
methods, and computer program products in accordance with
embodiments of the present invention. The processor 410 (which can
optionally be part of the ultrasound system 50) communicates with
the memory 414 via an address/data bus 448. The processor 410 can
be any commercially available or custom microprocessor. The memory
414 is representative of the overall hierarchy of memory devices
containing the software and data used to implement the
functionality of the data processing system 405. The memory 414 can
include, but is not limited to, the following types of devices:
cache, ROM, PROM, EPROM, EEPROM, flash memory, SRAM, and DRAM.
[0111] As shown in FIG. 9, the memory 414 may include several
categories of software and data used in the data processing system
405: the operating system 452; the application programs 454; the
input/output (I/O) device drivers 458; the tissue stiffness
calculation module 100; the color-coded tissue stiffness module 115
and the data 456. The data 456 may include a table of operational
parameters, including force, area, strain, stress and/or Elasticity
Modulus. As will be appreciated by those of skill in the art, the
operating system 452 may be any operating system suitable for use
with a data processing system, such as OS/2, AIX, OS/390 or
System390 from International Business Machines Corporation, Armonk,
N.Y., Windows CE, Windows NT, Windows95, Windows98 or Windows2000,
Windows VISTA from Microsoft Corporation, Redmond, Wash., Unix or
Linux or FreeBSD, Palm OS from Palm, Inc., Mac OS from Apple
Computer, LabView, or proprietary operating systems. The I/O device
drivers 458 typically include software routines accessed through
the operating system 452 by the application programs 454 to
communicate with devices such as I/O data port(s), data 451, data
storage 456 and certain memory 414 components and/or the dispensing
system 420.
[0112] The application programs 454 are illustrative of the
programs that implement the various features of the data processing
system 405 and preferably include at least one application which
supports operations according to embodiments of the present
invention. Finally, the data 456 represents the static and dynamic
data used by the application programs 454, the operating system
452, the I/O device drivers 458, and other software programs that
may reside in the memory 414.
[0113] While the present invention is illustrated, for example,
with reference to the modules 100, 115 being application programs
in FIG. 9, as will be appreciated by those of skill in the art,
other configurations may also be utilized while still benefiting
from the teachings of the present invention. For example, the
module 100 and/or 115 may also or alternately be incorporated into
the operating system 452, the I/O device drivers 458 or other such
logical division of the data processing system 405. Thus, the
present invention should not be construed as limited to the
configuration of FIG. 9, which is intended to encompass any
configuration capable of carrying out the operations described
herein.
[0114] The I/O data port can be used to transfer information
between the data processing system 405 and a remote processor or
another computer system or a network (e.g., an intranet and/or the
Internet and/or PACS) or to other devices controlled by or in
communication with the processor. These components may be
conventional components such as those used in many conventional
data processing systems which may be configured in accordance with
the present invention to operate as described herein.
[0115] While the present invention is illustrated, for example,
with reference to particular divisions of programs, functions and
memories, the present invention should not be construed as limited
to such logical divisions. Thus, the present invention should not
be construed as limited to the configuration of FIG. 9 but is
intended to encompass any configuration capable of carrying out the
operations described herein.
[0116] The flowcharts, schematic illustrations and block diagrams
of certain of the figures herein illustrate the architecture,
functionality, and operation of possible implementations according
to the present invention. In this regard, each block in the flow
charts, schematic illustrations or block diagrams represents a
module, segment, or portion of code, which comprises one or more
executable instructions for implementing the specified logical
function(s). It should also be noted that in some alternative
implementations, the functions noted in the blocks may occur out of
the order noted in the figures. For example, two blocks shown in
succession may in fact be executed substantially concurrently or
the blocks may sometimes be executed in the reverse order,
depending upon the functionality involved.
[0117] FIG. 10 illustrates an ultrasound image of compressed target
tissue 500I and FIG. 11 illustrates this same image 500I with a
prophetic color-coded overlay of tissue elasticity (stiffness) 500c
of target tissue within the image.
EXAMPLES
[0118] To demonstrate proof of concept a polyvinyl alcohol cryogel
(PVA-C) phantom was created and analyzed using the device shown in
FIG. 1. During the validation study, the material was subjected to
stress using an ultrasound transducer and strain was assessed from
the ultrasound images using a manual measurement. FIG. 13 shows the
computed stress-strain curve on one gel sample. The measured
stress-strain curve was monotonic linear (R.sup.2>0.99), with an
inherent dampening offset of 2.4996 kPa. The Young's modulus in
this test was 30.291 kPa, which is similar to values for this
material that are reported in the literature. See, e.g., Fromageau
et al., "Estimation of polyvinyl alcohol cryogel mechanical
properties with four ultrasound elastography methods and comparison
with gold standard testings," Ultrasonics, Ferroelectrics and
Frequency Control, IEEE Transactions on, vol. 54, no. 3, pp.
498-509, March 2007 and Fromageau et al., "Characterization of PVA
cryogel for intravascular ultrasound elasticity imaging,"
Ultrasonics, Ferroelectrics and Frequency Control, IEEE
Transactions on, vol. 50, no. 10, pp. 1318-1324, October 2003.
[0119] Further material testing was conducted using Ecoflex.RTM.
00-30, a platinum-catalyzed silicone. Using a Bose ElectroForce
3200, various compression tests were performed and the results
indicated a Young's modulus of 53.02 kPa at approximately a 10
percent strain. Testing was conducted as in the previous PVA-C
study. However there was increased attenuation of the ultrasound
signal as a result of large amounts of air bubbles cast within the
Ecoflex.RTM. 00-30. This resulted in an inaccurate ultrasound image
and thus an invalid measurement of the material deformation (FIG.
12). To eliminate the signal attenuation, the deformation of the
Ecoflex.RTM. 00-30 was measured by hand using a standard ruler and
the Young's modulus was determined to be 57.39 kPa at approximately
a 9 percent strain. The discrepancy in the Young's modulus value
calculated using the Bose ElectroForce 3200 and the determined
value is likely due to the limitations of the deformation
measurement not on the reliability or accuracy of the force
measurement as the stress values were within 0.1 kPa of one
another.
[0120] While the foregoing written description of the invention
enables one of ordinary skill to make and use what is considered
presently to be the best mode thereof, those of ordinary skill will
understand and appreciate the existence of variations,
combinations, and equivalents of the specific embodiment, method,
and examples herein. The invention should therefore not be limited
by the above described embodiment, method, and examples, but by all
embodiments and methods within the scope and spirit of the
invention as claimed.
* * * * *