U.S. patent application number 13/668047 was filed with the patent office on 2013-05-16 for sem scanner sensing apparatus, system and methodology for early detection of ulcers.
This patent application is currently assigned to BRUIN BIOMETRICS, LLC. The applicant listed for this patent is BRUIN BIOMETRICS, LLC, THE REGENTS OF THE UNIVERSITY OF CALIF. Invention is credited to Barbara M. Bates-Jensen, Joseph Boystak, Michael Flesch, William Kaiser, Yeung Lam, Alireza Mehrnia, Majid Sarrafzadeh, Frank Wang.
Application Number | 20130123587 13/668047 |
Document ID | / |
Family ID | 44914913 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130123587 |
Kind Code |
A1 |
Sarrafzadeh; Majid ; et
al. |
May 16, 2013 |
SEM SCANNER SENSING APPARATUS, SYSTEM AND METHODOLOGY FOR EARLY
DETECTION OF ULCERS
Abstract
A handheld, conforming capacitive sensing apparatus configured
to measure Sub-Epidermal Moisture (SEM) as a mean to detect and
monitor the formation of pressure ulcers. The device incorporates
an array of electrodes which are excited to measure and scan SEM in
a programmable and multiplexed manner by a battery-less RF-powered
chip. The scanning operation is initiated by an interrogator which
excites a coil embedded in the apparatus and provides the needed
energy burst to support the scanning/reading operation. Each
electrode measures the equivalent sub-epidermal capacitance
corresponding and representing the moisture content.
Inventors: |
Sarrafzadeh; Majid; (Anaheim
Hills, CA) ; Kaiser; William; (Los Angeles, CA)
; Mehrnia; Alireza; (Los Angeles, CA) ;
Bates-Jensen; Barbara M.; (Pasadena, CA) ; Wang;
Frank; (Cupertino, CA) ; Flesch; Michael;
(Beverly Hills, CA) ; Boystak; Joseph; (Marina Del
Rey, CA) ; Lam; Yeung; (Sherman Oaks, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
THE UNIVERSITY OF CALIF; THE REGENTS OF
BRUIN BIOMETRICS, LLC; |
Oakland
Los Angeles |
CA
CA |
US
US |
|
|
Assignee: |
BRUIN BIOMETRICS, LLC
Los Angeles
CA
THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
Oakland
CA
|
Family ID: |
44914913 |
Appl. No.: |
13/668047 |
Filed: |
November 2, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/US2011/035618 |
May 6, 2011 |
|
|
|
13668047 |
|
|
|
|
61332755 |
May 8, 2010 |
|
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|
61453852 |
Mar 17, 2011 |
|
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Current U.S.
Class: |
600/306 |
Current CPC
Class: |
A61B 2562/164 20130101;
A61B 2562/0247 20130101; A61B 5/443 20130101; A61B 5/6844 20130101;
A61B 5/447 20130101; A61B 2562/0214 20130101; A61B 5/6843 20130101;
A61B 2562/046 20130101; A61B 5/0533 20130101; A61B 5/445 20130101;
A61B 2562/04 20130101; A61B 5/7285 20130101; A61B 2562/066
20130101; A61B 5/7271 20130101; A61B 5/05 20130101; A61B 5/0537
20130101 |
Class at
Publication: |
600/306 |
International
Class: |
A61B 5/00 20060101
A61B005/00; A61B 5/053 20060101 A61B005/053 |
Claims
1. An apparatus for sensing sub-epidermal moisture from a location
external to a patient's skin, comprising: a bipolar RF sensor
embedded on a flexible substrate; a conformal pressure pad disposed
adjacent and underneath the substrate; wherein the conformal
pressure pad is configured to support the flexible substrate while
allowing the flexible substrate to conform to a non-planar sensing
surface of the patient's skin; and interface electronics coupled to
the sensor; wherein said interface electronics are configured to
control emission and reception of RF energy to interrogate the
patient's skin.
2. An apparatus as recited in claim 1, further comprising: an
annular spacer adjacent and underneath the conformal pressure pad;
wherein the annular spacer comprises a central opening configured
to allow the conformal pressure pad to deflect freely into the
central opening.
3. An apparatus as recited in claim 1, further comprising: an array
of bipolar RF sensors spaced across the flexible substrate; wherein
each of the sensors is independently coupled to the interface
electronics to independently interrogate the patient's skin.
4. An apparatus as recited in claim 3: wherein each of the sensors
is configured to measure an equivalent sub-epidermal capacitance of
a target region of skin; said sub-epidermal capacitance
corresponding to the moisture content of the target region of
skin.
5. An apparatus as recited in claim 4: wherein the array of sensors
comprises a first sensor having a first contact area and a second
sensor having a second contact area larger than the first sensor;
and wherein the first and second sensors interrogate the skin at
different depths.
6. An apparatus as recited in claim 4: wherein the substrate
comprises a substrate assembly comprising a substrate layer; and
wherein the sensor comprises a sensing pad having a first electrode
embedded on a first side of the substrate and a second electrode
embedded on a second side of the substrate.
7. An apparatus as recited in claim 6, further comprising a
biocompatible cover layer disposed over said first side of said
substrate layer.
8. An apparatus as recited in claim 6, further comprising a cover
layer disposed under said second side of said substrate layer.
9. An apparatus as recited in claim 6, further comprising: a
stiffener layer disposed under said second side of said substrate
layer; wherein the stiffener layer comprises a footprint
substantially similar to that of the sensor array.
10. An apparatus as recited in claim 6: wherein said first
electrode comprises an annular ring having an inner radius and an
outer radius; wherein said second electrode comprises an outer
radius having a smaller diameter than the inner radius of the first
electrode; and wherein said second electrode is concentric with
said first radius.
11. An apparatus as recited in claim 1, wherein the interface
electronics are configured to transmit data retrieved from said
sensors.
12. An apparatus as recited in claim 4, further comprising: a
pressure sensor positioned in line with said RF sensor; said
pressure sensor configured to measure an applied pressure of the
substrate at a location on the patient's skin.
13. An apparatus as recited in claim 1, wherein the flexible
substrate comprises Kapton or Polyimide.
14. A scanner for sensing sub-epidermal moisture from a location
external to a patient's skin, comprising: an array of bipolar RF
sensors embedded on a flexible substrate; and a conformal pressure
pad disposed adjacent and underneath the substrate; wherein the
conformal pressure pad is configured to support the flexible
substrate while allowing the flexible substrate to conform to a
non-planar sensing surface of the patient's skin; wherein said
sensor array is configured to emit and receive RF energy to
interrogate the patient's skin; and wherein each of the sensors are
independently are individually wired to independently interrogate
the patient's skin.
15. A scanner as recited in claim 14, further comprising: interface
electronics coupled to the sensor; wherein said interface
electronics is configured to control the emission and reception of
RF energy.
16. A scanner as recited in claim 14, further comprising: an
annular spacer adjacent and underneath the conformal pressure pad;
wherein the annular spacer comprises a central opening configured
to allow the conformal pressure pad to deflect freely into the
central opening.
17. A scanner as recited in claim 14: wherein each of the sensors
is configured to measure an equivalent sub-epidermal capacitance of
a target region of skin; said sub-epidermal capacitance
corresponding to the moisture content of the target region of
skin.
18. A scanner as recited in claim 14: wherein the array of sensors
comprises a first sensor having a first contact area and a second
sensor having a second contact area larger than the first sensor;
and wherein the first and second sensors interrogate the skin at
different depths.
19. A scanner as recited in claim 14: wherein each sensor comprises
a first electrode in the form of an annular ring having an inner
radius and an outer radius and a second electrode comprising an
outer radius having a smaller diameter than the first electrode;
and wherein said second electrode is concentric with said first
radius.
20. A scanner as recited in claim 19: wherein the substrate
comprises a substrate assembly comprising a substrate layer; and
wherein the first electrode is embedded on a first side of the
substrate and the second electrode embedded on a second side of the
substrate.
21. A scanner as recited in claim 20, further comprising: an upper
biocompatible cover layer disposed over said first side of said
substrate layer and a lower cover layer disposed under said second
side of said substrate layer.
22. A scanner as recited in claim 20, further comprising: a
stiffener layer disposed under said second side of said substrate
layer; wherein the stiffener layer comprises a footprint
substantially similar to that of the sensor array.
23. A scanner as recited in claim 14, further comprising: an array
of pressure sensors positioned in line with said RF sensor; said
pressure sensors are configured to measure an applied pressure of
the substrate at corresponding locations on the patient's skin.
24. A method for monitoring the formation of pressure ulcers at a
target location of a patient's skin, comprising: positioning a
flexible substrate adjacent the target location of the patient's
skin; the flexible substrate comprising one or more bipolar RF
sensors; conforming the flexible substrate to the patient's skin at
the target location; exciting the one or more bipolar RF sensors to
emit RF energy into the patient's skin; and measuring the
capacitance of the skin at the target location as an indicator of
the Sub-Epidermal Moisture (SEM) at the target location.
25. A method as recited in claim 24: wherein the one or more
sensors comprise an array of sensors disposed across said
substrate; and wherein the one or more sensors are individually
controlled to independently excite the one or more sensors.
26. A method as recited in claim 24, further comprising: measuring
an applied pressure of the substrate at the target location on the
patient's skin.
27. A method as recited in claim 25, further comprising: measuring
an applied pressure of the substrate on the patient's skin at each
of the sensors in the array.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a 35 U.S.C. .sctn.111(a) continuation of
PCT international application number PCT/US2011/035618 filed on May
6, 2011, incorporated herein by reference in its entirety, which is
a nonprovisional of U.S. provisional patent application Ser. No.
61/332,755 filed on May 8, 2010, incorporated herein by reference
in its entirety, and a nonprovisional of U.S. provisional patent
application Ser. No. 61/453,852 filed on Mar. 17, 2011,
incorporated herein by reference in its entirety. Priority is
claimed to each of the foregoing applications.
[0002] The above-referenced PCT international application was
published as PCT International Publication No. WO 2011/143071on
Nov. 17, 2011 and republished on Apr. 5, 2012, and is incorporated
herein by reference in its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0003] Not Applicable
INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT
DISC
[0004] Not Applicable
NOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTION
[0005] A portion of the material in this patent document is subject
to copyright protection under the copyright laws of the United
States and of other countries. The owner of the copyright rights
has no objection to the facsimile reproduction by anyone of the
patent document or the patent disclosure, as it appears in the
United States Patent and Trademark Office publicly available file
or records, but otherwise reserves all copyright rights whatsoever.
The copyright owner does not hereby waive any of its rights to have
this patent document maintained in secrecy, including without
limitation its rights pursuant to 37 C.F.R. .sctn.1.14.
BACKGROUND OF THE INVENTION
[0006] 1. Field of the Invention
[0007] This invention pertains generally to monitoring skin
pressure ulcers and more particularly to skin ulcer monitoring via
measurement of Sub-epidermal Moisture (SEM).
[0008] 2. Description of Related Art
[0009] Patients' skin integrity has long been an issue of concern
for nurses and in nursing homes. Maintenance of skin integrity has
been identified by the American Nurses Association as an important
indicator of quality nursing care. Meanwhile, pressure ulcers
remain a major health problem particularly for hospitalized older
adults. When age is considered along with other risk factors, the
incidence of pressure ulcers is significantly increased. Overall
incidence of pressure ulcers for hospitalized patients ranges from
2.7% to 29.5%, and rates of greater than 50% have been reported for
patients in intensive care settings. In a multicenter cohort
retrospective study of 1,803 older adults discharged from acute
care hospitals with selected diagnoses, 13.2% (i.e., 164 patients)
demonstrated an incidence of stage I ulcers. Of those 164 patients,
38 (16%) had ulcers that progressed to a more advanced stage.
Pressure ulcers additionally have been associated with an increased
risk of death one year after hospital discharge. The estimated cost
of treating pressure ulcers ranges from $5,000 to $40,000 for each
ulcer, depending on severity.
[0010] Therefore, there is an urgent need to develop a preventive
solution to measure moisture content of the skin as a mean to
detect early symptoms of ulcer development.
BRIEF SUMMARY OF THE INVENTION
[0011] An aspect of the present invention is a smart compact
capacitive sensing conforming handheld apparatus configured to
measure Sub-epidermal Moisture (SEM) as a mean to detect and
monitor the development of pressure ulcers. The device incorporates
an array of electrodes which are excited to measure and scan SEM in
a programmable and multiplexed manner by a battery-less RF-powered
chip. The scanning operation is initiated by an interrogator which
excites a coil embedded in the apparatus and provides the needed
energy burst to support the scanning/reading operation. Each
embedded electrode measures the equivalent sub-epidermal
capacitance corresponding and representing the moisture content of
the target surface.
[0012] An aspect of this invention is the in situ sensing and
monitoring of skin or wound or ulcer development status using a
wireless, biocompatible RF powered capacitive sensing system
referred to as smart SEM imager. The present invention enables the
realization of smart preventive measures by enabling early
detection of ulcer formation or inflammatory pressure which would
otherwise have not been detected for an extended period with
increased risk of infection and higher stage ulcer development.
[0013] In one beneficial embodiment, the handheld capacitive
sensing imager apparatus incorporates pressure sensing components
in conjunction with the sensing electrodes to monitor the level of
applied pressure on each electrode in order to guarantee precise
wound or skin electrical capacitance measurements to characterize
moisture content. In summary, such embodiment would enable new
capabilities including but not limited to: 1) measurement
capabilities such as SEM imaging and SEM depth imaging determined
by electrode geometry and dielectrics, and 2) signal processing and
pattern recognition having automatic and assured registration
exploiting pressure imaging and automatic assurance of usage
exploiting software systems providing usage tracking.
[0014] One major implication of this sensor-enhanced paradigm is
the ability to better manage each individual patient resulting in a
timelier and more efficient practice in hospitals and even nursing
homes. This is applicable to patients with a history of chronic
wounds, diabetic foot ulcers, pressure ulcers or post-operative
wounds. In addition, alterations in signal content may be
integrated with the activity level of the patient, the position of
patient's body and standardized assessments of symptoms. By
maintaining the data collected in these patients in a signal
database, pattern classification, search, and pattern matching
algorithms can be developed to better map symptoms with alterations
in skin characteristics and ulcer development. This approach is not
limited to the specific condition of ulcer or wound, but may have
broad application in all forms of wound management and even skin
diseases or treatments.
[0015] One aspect is apparatus for sensing sub-epidermal moisture
(SEM) from a location external to a patient's skin. The apparatus
includes a bipolar RF sensor embedded on a flexible substrate, and
a conformal pressure pad disposed adjacent and underneath the
substrate, wherein the conformal pressure pad is configured to
support the flexible substrate while allowing the flexible
substrate to conform to a non-planar sensing surface of the
patient's skin. The apparatus further includes interface
electronics coupled to the sensor; wherein the interface
electronics are configured to control emission and reception of RF
energy to interrogate the patient's skin.
[0016] Another aspect is a method for monitoring the formation of
pressure ulcers at a target location of a patient's skin. The
method includes the steps of positioning a flexible substrate
adjacent the target location of the patient's skin; the flexible
substrate comprising one or more bipolar RF sensors; conforming the
flexible substrate to the patient's skin at the target location;
exciting the one or more bipolar RF sensor to emit RF energy into
the patient's skin; and measuring the capacitance of the skin at
the target location as an indicator of the Sub-Epidermal Moisture
(SEM) at the target location.
[0017] Further aspects of the invention will be brought out in the
following portions of the specification, wherein the detailed
description is for the purpose of fully disclosing preferred
embodiments of the invention without placing limitations
thereon.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0018] The invention will be more fully understood by reference to
the following drawings which are for illustrative purposes
only:
[0019] FIG. 1 illustrates an assembled perspective component view
of the SEM Scanner of the present invention.
[0020] FIG. 2 illustrates a perspective view of a Kapton-based
conforming sensing substrate assembly of the present invention.
[0021] FIG. 3 shows a top view of an exemplary concentric sensing
electrode in accordance with the present invention.
[0022] FIG. 4 illustrates a side view of a flex stack-up for the
Kapton-based conforming sensing substrate shown in FIG. 2.
[0023] FIG. 5 illustrates a side view of an alternative flex
stack-up for a Kapton-based conforming sensing substrate.
[0024] FIG. 6 shows a top view of two-electrode sensing
Kapton-based flex sensor substrates for three alternative types of
capacitive sensing concentric electrodes.
[0025] FIG. 7 illustrates an exploded perspective component view of
the SEM scanner of FIG. 1.
[0026] FIG. 8 illustrates a schematic side view of the SEM scanner
of FIG. 1.
[0027] FIG. 9 illustrates a schematic side view of the SEM scanner
of FIG. 8 in contact with subject skin.
[0028] FIG. 10 illustrates a perspective view of an assembled SEM
scanner with an alternative array of sensors in accordance with the
present invention.
[0029] FIG. 11 is a plot of normalized responses of the tested
electrodes of the present invention.
[0030] FIG. 12 is a graph of measured equivalent capacitance for
dry volar arm for three different concentric sensor electrodes.
[0031] FIG. 13 is a plot of time dependent fractional change in
capacitance relative to dry skin for three different concentric
sensor electrodes (after 30 minutes of applying lotion).
[0032] FIG. 14 is a plot of time dependent fractional change in
capacitance relative to dry skin for three different concentric
sensor electrodes (after 15 minutes of applying lotion).
[0033] FIG. 15 is a plot of fractional change vs. time.
[0034] FIG. 16 shows a SEM scanner electrode system and electrode
layering providing proper shielding from interference.
[0035] FIG. 17 shows an SEM scanner mechanical compliance for
electrodes developed to enable probing of bony prominence.
DETAILED DESCRIPTION OF THE INVENTION
[0036] In one exemplary embodiment, a smart handheld capacitive
sensing device according to the present invention employs a
programmable sensing electrode array. This is based on methods that
use an interrogator to excite the embedded electrodes.
[0037] FIG. 1 illustrates an SEM scanning/sensing apparatus 10
according to the present invention. The scanner 10 comprises five
main components, including a top silicone edge sealing gasket 18
encircling a Kapton-based sensing substrate 16, which rests on a
conformal silicone pressure pad 12. A thick annular silicone spacer
20 is disposed under pressure pad to provide free space for the
pressure pad to deform. The bottom layer comprises an interface
electronics package enclosure 22 that houses interface circuitry
for interrogating and transmitting data for evaluation. These five
main components are described in further detail below.
[0038] In the embodiment shown in FIG. 1, an array 14 of individual
RF electrode sensors 24 and 26 is embedded on a flexible
biocompatible substrate 16. Substrate 16 may comprise a laminated
Kapton (Polyimide) chip-on-flex.
[0039] FIG. 2 illustrates one embodiment of a Kapton sensor
substrate 16a that comprises an array 14 of differing sized
concentric sensing electrodes. A flexible biocompatible Polyimide
or Kapton substrate 32 comprises a layer of sensing pads 14 and 15
coated on one side with an ultra thin cover layer 30 of Polyimide
(e.g. CA335) to isolate pads electrodes 14,15 from direct moisture
contact and also to provide a uniform contact surface.
[0040] In FIG. 2, sample capacitive sensing electrodes 14 are shown
in different sizes (e.g. 24, 26, and 29), which are manipulated to
achieve and sense different depths of skin. Sensing electrodes 14
may comprise any number of different shape and configurations, such
as the concentric circles of array 14, or the interdigitating
fingers of sensor 15.
[0041] FIG. 3 illustrates a close-up top view of a concentric
sensing pad 26 in accordance with the present invention. Pad 26
comprises a bipolar configuration having a first electrode 36
comprising an outer annular ring disposed around a second inner
circular electrode 38. Outer ring electrode 36 has an outer
diameter D.sub.o and an inner diameter D.sub.i that is larger than
the diameter D.sub.c of the circular inner electrode 38 to form
annular gap 40. Inner circular electrode 38 and outer ring
electrode 36 are coupled electrically to interface electronics in
the interface electronics package 22. As shown in greater detail in
FIGS. 4 and 5, electrodes 36 and 38 are disposed on separate layers
within the substrate assembly 16.
[0042] The dimensions of the sensor pads 24, 26 generally
correspond to the depth of interrogation into the derma of the
patient. Accordingly, a larger diameter pad (e.g. pad 26 or 29)
will penetrate deeper into the skin than a smaller pad. The desired
depth may vary depending on the region of the body being scanned,
or the age, skin anatomy or other characteristic of the patient.
Thus, SEM scanner 10 may comprise an array of different sized pads
(e.g. small pads 24 and medium sized pads 26 shown in FIG. 1) each
individually coupled to the interface electronics package 22.
[0043] FIG. 4 illustrates side view of a flex stack-up for a Kapton
based substrate assembly 16, where thin adhesive layers 42 are used
to attach a Kapton layer 32 in between copper layers 44 and 46, all
of which are disposed between upper coverlay 30 and lower coverlay
48. A stiffener 50 is disposed under lower coverlay 48, being
positioned directly under copper layer 46 of the sensing pads. The
stiffener 50 forms a rigid portion of the substrate where sensing
pad array 14, connectors (e.g. connectors 66, 76, or 86 shown in
FIG. 6) and interfacing (e.g. lead wires 34) are located, so that
these areas do not deform, whereas the rest of the substrate is
free to deform. The top copper layer 44 is used to etch out
electrode array 14 and corresponding copper routing 34 to the
connectors. The bottom copper layer 46 preferably comprises a
crisscross ground plane to shield electrode array 14 from unwanted
electromagnetic interference.
[0044] In one embodiment, the flex substrate 16 assembly
comprises
[0045] Pyralux FR material from Dupont. In an exemplary
configuration, approximately 5 mil thick FR9150R double-sided
Pyralux FR copper clad laminate is used as the Kapton substrate.
Top coverlay 30 comprises Pyralux 5 mil FR0150 and the bottom
coverlay 48 comprises 1 mil FR0110 Pyralux. The thickness of the
top FR0150 coverlay 30 is an important parameter as it affects the
sensitivity of sensing electrodes in measuring skin moisture
content. Copper layers 44, 46 are generally 1.4 mil thick, while
adhesive layers 42 are generally 1 mil thick. The stiffener 50 is
shown in FIG. 4 is approximately 31 mil thick.
[0046] FIG. 5 shows a side view of a preferred alternative flex
stack-up for a Kapton based substrate 120, where thin adhesive
layers 42 (1 mil) are used to attach an 18 mil Kapton layer 122 in
between 1.4 mil copper layers 44 and 46, all of which are disposed
between 2 mil upper coverlay 30 and 1 mil lower coverlay 48. A
stiffener 50 is disposed under lower coverlay 48, being positioned
directly under copper layer 46 of the sensing pad. The 31 mil FR4
stiffener 126 forms a rigid portion of the substrate under the
array 14 of sensing pads, connectors 66 and interfacing 34. A 2 mil
layer of PSA adhesive 124 is used between the bottom coverlay 48
and stiffener 126. The layering of assembly 120 is configured to
provide proper shielding from interference.
[0047] FIG. 6 shows a top view of three separate and adjacently
arranged concentric bipolar electrode sensing Kapton-based flex
pads 60, 70 and 80 having different sized capacitive sensing
concentric electrodes. Pad 60 comprises a substrate having two
large concentric electrodes 62 wired through substrate 64 via
connectors 34 to lead line inputs 66. Pad 70 comprises a substrate
having two medium concentric electrodes 72 wired through substrate
74 to lead line inputs 76. Pad 80 comprises a substrate having two
small concentric electrodes 82 wired through substrate 84 to lead
line inputs 86. The configuration shown in FIG. 6 is optimized for
cutting/manufacturing and also to avoid interference between data
lines and sensors. Each of the bipolar electrode pads is
individually wired to the electronics package 22 to allow for
independent interrogation, excitation, and data retrieval.
[0048] FIG. 7 illustrates an exploded perspective component view of
the SEM scanner 10. The silicone edge sealing gasket 18 is applied
over the Kapton sensor substrate assembly 16 to seal and shield the
edge interface connectors through which interface electronics
package 22 excite and controls the sensing electrode array 14. The
Kapton sensor substrate assembly 16 rests on a conformal silicone
pressure pad 12 that provides both support and conformity to enable
measurements over body curvature and bony prominences.
[0049] In one beneficial embodiment, pressure sensor 11 may be
embedded under each sensing electrode 24, 26 (e.g. in an identical
array not shown), sandwiched between Kapton sensor substrate 26 and
the conformal silicone pressure pad 28 to measure applied pressure
at each electrode, thus ensuring a uniform pressure and precise
capacitance sensing.
[0050] Lead access apertures 28 provide passage for routing the
connector wires (not shown) from the substrate connectors (e.g. 66,
76, 86) through the pressure pad 12, annular spacer 20 to the
interface electronics 22.
[0051] The annular silicone spacer 20 comprises a central opening
27 that provides needed spacing between the conformal silicone
pressure pad 12 and the interface electronics package 22 to allow
the pressure pad 12 and flexible substrate to conform in a
non-planar fashion to conduct measurements over body curvatures or
bony prominences.
[0052] In one embodiment, the interface electronics package 22 is
connected to a logging unit or other electronics (not shown)
through wire-line USB connector 56.
[0053] The interface electronics package 22 preferably comprises an
enclosure that contains all the electronics (not shown) needed to
excite, program and control the sensing operation and manage the
logged data. The electronics package 22 may also comprise Bluetooth
or other wireless communication capabilities to allow for transfer
of sensing data to a computer or other remote device. Docked data
transfer is also contemplated, in addition to real-time Bluetooth
transfer. A gateway device (not shown) may be used for
communicating with the SEM device 10 and data formatting prior to
upload to a computer or backend server.
[0054] FIG. 8 is a schematic side view of the SEM scanner 10 in the
nominal configuration, showing the edge gasket 18 over Kapton
substrate 16, and lead access apertures 28, which provide access
through annular spacer 20 and conformal pad 12 to electronics
22.
[0055] FIG. 9 illustrates a schematic side view of the SEM scanner
10 in contact with the target subject 25. The annular silicone
spacer 20 provides enough spacing for conforming silicone pad 12 to
conform to the target surface 25. The conforming silicone pad 12
enables continuous contact between the substrate 16 and patient's
skin 25, thus minimizing gaps between the substrate 16 and
patient's skin 25 that could otherwise result in improper readings
of the patient anatomy. Electrode array 14, which is embedded in
substrate 16, is shown interrogating into the derma of tissue 25 by
directing emission of an RF signal or energy into the skin and
receiving the signal and correspondingly reading the reflected
signal. The interrogator or electronics package 22 excites
electrode coil 14 by providing the needed energy burst to support
the scanning/reading of the tissue. Each embedded electrode 14
measures the equivalent sub-epidermal capacitance corresponding to
the moisture content of the target skin 25.
[0056] While other energy modalities are contemplated (e.g.
ultrasound, microwave, etc.), RF is generally preferred for its
resolution in SEM scanning.
[0057] FIG. 10 illustrates a perspective view of an assembled SEM
scanner 10 with an alternative substrate 16b having an array 14 of
ten sensors dispersed within the substrate 16b. This larger array
14 provides for a larger scanning area of the subject anatomy, thus
providing a complete picture of the target anatomy in one image
without having to generate a scanning motion. It is appreciated
that array 14 may comprise any number of individual sensors, in be
disposed in a variety of patterns.
[0058] The SEM scanner 10 was evaluated using a number of different
sized and types of sensors 26. Table 1 illustrates electrode
geometries are used throughout the following measurements. As shown
in FIG. 1 the outer ring electrode diameter D.sub.o varied from 5
mm for the XXS pad, to 55 mm for the large pad. The outer ring
electrode inner diameter D.sub.i varied from 4 mm for the XXS pad,
to 40 mm for the large pad. The inner electrode diameter D.sub.C
varied from 2 mm for the XXS pad, to 7 mm for the large pad. It is
appreciated that the actual dimensions of the electrodes may vary
from ranges shown in these experiments. For example, the contact
diameter may range from 5 mm to 30 mm, and preferably ranges from
10 mm to 20 mm.
[0059] To measure the properties of each sensor size listed in
Table 1, the sensors were fabricated using both Kapton and rigid
board. In testing with the rigid sensor pads, lotion was applied to
the thumb continuously for 15 minutes.
[0060] FIG. 11 is a plot of normalized responses of the tested
electrodes of the present invention. The four sensors' (XXS, XS, S,
M) normalized responses are compared in FIG. 11 and Table 2.
[0061] As can be seen in FIG. 11 and Table 2, the S electrode
appears to be most responsive overall to the presence of moisture.
Both the M and S electrodes seem to exhibit a peak. This suggests a
depth dependency of the moisture being absorbed into the skin, as
the roll-off from the M electrode occurs about 5 minutes after the
peak for S electrode.
[0062] The SEM scanner 10 was also tested on the inner arm. A
resistive pressure sensor (e.g. sensor 11 shown in FIG. 7) was also
used to measure pressure applied on sensor to the arm. This way,
constant pressure is applied across measurements. First, the dry
inner arm was measured using the XS, S and M electrodes. Then, the
same area was masked off with tape, and moisturizer lotion was
applied for 30 minutes. Subsequent measurements were made on the
same location after cleaning the surface.
[0063] FIG. 12 is a graph of measured equivalent capacitance for
dry Volar arm for three different sized (M, S, XS) concentric
sensor electrodes before applying the commercial lotion
moisturizer.
[0064] FIG. 13 is a plot of time dependent fractional change in
capacitance relative to dry skin for three different concentric
sensor electrodes (after 30 minutes of applying lotion).
[0065] FIG. 14 is a plot of time dependent fractional change in
capacitance relative to dry skin for three different concentric
sensor electrodes (after 15 minutes of applying lotion) on two
subjects. This experiment was performed with faster sampling
intervals and with lotion applied for 15 minutes only on forearms
of two test subjects. Again, a resistive pressure sensor was used
to measure pressure applied on sensor to the arm. This way,
constant pressure is applied across measurements. First the dry
inner arm was measured using the XS, S and M electrodes. Then the
same area was masked off with tape, and lotion was applied for 15
minutes. Subsequent measurements were made on the same location
every 5 minutes. Pressure was maintained at 50 k Ohms, and the
forearm was tested again. We noticed an interesting observation for
the case "F" in comparison to case "A" and also compared to
previous measurements. Case "F" took a shower right before running
the measurements and hence as a result his skin was relatively
saturated with moisture. As a result, we observed less degree of
sensitivity to the applied deep moisturizer for case "F".
[0066] The experiment was performed again for case "F", with a time
resolution of 3 minutes, knowing that the subject did not shower in
the morning before the test. The lotion was applied to the inner
forearm for 15 minutes. Pressure was maintained at 50 k Ohms. The
results confirm the sensitivity of the measurement to the residual
skin moisture.
[0067] FIG. 15 is a plot of results for fractional change vs. time
for M, S and XS electrodes.
[0068] FIG. 16 shows a preferred embodiment of a layered SEM
scanner electrode system 100 having a first electrode pad 102 and
second electrode pad 104. Pad 104 is connected to lead line inputs
116 via wiring 34 along curved path 112. Pad 102 is connected to
lead line inputs 110 via wiring 34 along curved path 106. A
stiffener layer (e.g. layer 126 in FIG. 5) is provided directly
under lead inputs 110 and 116 (see footprint 108 and 114
respectively) and under pads 102 and 104 (see footprint 122 and 120
respectively).
[0069] In this embodiment, the electrode size is approximately 2300
in width by 3910 mil in height.
[0070] FIG. 17 illustrates the SEM Scanner mechanical compliance
(force-displacement relationship) for electrodes of system 100,
developed to enable probing of bony prominence. The diamond symbols
show the upper electrode 104 response, square symbols show the
lower electrode 102 response.
[0071] The SEM scanner device 10 may also include other
instruments, such as a camera (not shown), which can be used to
take pictures of the wound, or develop a scanning system to scan
barcodes as a login mechanism or an interrogator.
[0072] Patients using the SEM scanner device 10 may wear a bracelet
(not shown) that contains data relating to their patient ID. This
ID can be scanned by the camera embedded in the SEM scanner 10 to
confirm correct patient ID correspondence. Alternatively, a
separate RF scanner (not shown) may be used for interrogating the
bracelet (in addition to the camera).
[0073] The SEM scanner device 10 is preferably ergonomically shaped
to encourage correct placement of the device on desired body
location.
[0074] The SEM Scanner device 10 of the present invention is
capable of generating physical, absolute measurement values, and
can produce measurements at multiple depths.
[0075] From the foregoing it will be appreciated that the present
invention can be embodied in various ways, which include but are
not limited to the following:
[0076] 1. An apparatus for sensing sub-epidermal moisture from a
location external to a patient's skin, comprising: a bipolar RF
sensor embedded on a flexible substrate; a conformal pressure pad
disposed adjacent and underneath the substrate; wherein the
conformal pressure pad is configured to support the flexible
substrate while allowing the flexible substrate to conform to a
non-planar sensing surface of the patient's skin; and interface
electronics coupled to the sensor; wherein said interface
electronics is configured to control emission and reception of RF
energy to interrogate the patient's skin.
[0077] 2. The apparatus of embodiment 1, further comprising: an
annular spacer adjacent and underneath the conformal pressure pad;
wherein the annular spacer comprises a central opening configured
to allow the conformal pressure pad to deflect freely into the
central opening.
[0078] 3. The apparatus of embodiment 1, further comprising: an
array of bipolar RF sensors spaced across the flexible substrate;
wherein each of the sensors is independently coupled to the
interface electronics to independently interrogate the patient's
skin.
[0079] 4. The apparatus of embodiment 3: wherein each of the
sensors is configured to measure an equivalent sub-epidermal
capacitance of a target region of skin; said sub-epidermal
capacitance corresponding to the moisture content of the target
region of skin.
[0080] 5. The apparatus of embodiment 4: wherein the array of
sensors comprises a first sensor having a first contact area and a
second sensor having a second contact area larger than the first
sensor; wherein the first and second sensors interrogate the skin
at different depths.
[0081] 6. The apparatus of embodiment 4: wherein the substrate
comprises a substrate assembly comprising a substrate layer; and
wherein the sensor comprises a sensing pad having a first electrode
embedded on a first side of the substrate and a second electrode
embedded on a second side of the substrate.
[0082] 7. The apparatus of embodiment 6, further comprising a
biocompatible cover layer disposed over said first side of said
substrate layer.
[0083] 8. The apparatus of embodiment 6, further comprising a cover
layer disposed under said second side of said substrate layer.
[0084] 9. The apparatus of embodiment 6, further comprising a
stiffener layer disposed under said second side of said substrate
layer; wherein the stiffener layer comprises a footprint
substantially similar to that of the sensor array.
[0085] 10. The apparatus of embodiment 6: wherein said first
electrode comprises an annular ring having an inner radius and an
outer radius; wherein said second electrode comprises an outer
radius having a smaller diameter than the inner radius of the first
electrode; and wherein said second electrode is concentric with
said first radius.
[0086] 11. The apparatus of embodiment 1, wherein the interface
electronics are configured to transmit data retrieved from said
sensors.
[0087] 12. The apparatus of embodiment 4, further comprising: a
pressure sensor positioned in line with said RF sensor; said
pressure sensor configured to measure an applied pressure of the
substrate at a location on the patient's skin.
[0088] 13. The apparatus of embodiment 1, wherein the flexible
substrate comprises Kapton or Polyimide.
[0089] 14. A scanner for sensing sub-epidermal moisture from a
location external to a patient's skin, comprising: an array of
bipolar RF sensors embedded on a flexible substrate; and a
conformal pressure pad disposed adjacent and underneath the
substrate; wherein the conformal pressure pad is configured to
support the flexible substrate while allowing the flexible
substrate to conform to a non-planar sensing surface of the
patient's skin; wherein said sensor array is configured to emit and
receive RF energy to interrogate the patient's skin; and wherein
each of the sensors are independently are individually wired to
independently interrogate the patient's skin.
[0090] 15. The scanner of embodiment 14, further comprising:
interface electronics coupled to the sensor; wherein said interface
electronics is configured to control the emission and reception of
RF energy.
[0091] 16. The scanner of embodiment 14, further comprising: an
annular spacer adjacent and underneath the conformal pressure pad;
wherein the annular spacer comprises a central opening configured
to allow the conformal pressure pad to deflect freely into the
central opening.
[0092] 17. The scanner of embodiment 14: wherein each of the
sensors is configured to measure an equivalent sub-epidermal
capacitance of a target region of skin; said sub-epidermal
capacitance corresponding to the moisture content of the target
region of skin.
[0093] 18. The scanner of embodiment 14: wherein the array of
sensors comprises a first sensor having a first contact area and a
second sensor having a second contact area larger than the first
sensor; and wherein the first and second sensors interrogate the
skin at different depths.
[0094] 19. The scanner of embodiment 14: wherein each sensor
comprises a first electrode in the form of an annular ring having
an inner radius and an outer radius and a second electrode
comprising an outer radius having a smaller diameter than the first
electrode; and wherein said second electrode is concentric with
said first radius.
[0095] 20. The scanner of embodiment 19: wherein the substrate
comprises a substrate assembly comprising a substrate layer; and
wherein the first electrode is embedded on a first side of the
substrate and the second electrode embedded on a second side of the
substrate.
[0096] 21. The scanner of embodiment 20, further comprising: an
upper biocompatible cover layer disposed over said first side of
said substrate layer and a lower cover layer disposed under said
second side of said substrate layer.
[0097] 22. The scanner of embodiment 20, further comprising: a
stiffener layer disposed under said second side of said substrate
layer; wherein the stiffener layer comprises a footprint
substantially similar to that of the sensor array.
[0098] 23. The scanner of embodiment 14, further comprising: an
array of pressure sensors positioned in line with said RF sensor;
said pressure sensors are configured to measure an applied pressure
of the substrate at corresponding locations on the patient's
skin.
[0099] 24. A method for monitoring the formation of pressure ulcers
at a target location of a patient's skin, comprising: positioning a
flexible substrate adjacent the target location of the patient's
skin; the flexible substrate comprising one or more bipolar RF
sensors; conforming the flexible substrate to the patient's skin at
the target location; exciting the one or more bipolar RF sensor to
emit RF energy into the patient's skin; and measuring the
capacitance of the skin at the target location as an indicator of
the Sub-Epidermal Moisture (SEM) at the target location.
[0100] 25. The method of embodiment 24: wherein the one or more
sensors comprise an array of sensors disposed across said
substrate; and wherein the one or more sensors are individually
controlled to independently excite the one or more sensors.
[0101] 26. The method of embodiment 24, further comprising:
measuring an applied pressure of the substrate at the target
location on the patient's skin.
[0102] 27. The method of embodiment 25, further comprising:
measuring an applied pressure of the substrate on the patient's
skin at each of the sensors in the array.
[0103] Although the description above contains many details, these
should not be construed as limiting the scope of the invention but
as merely providing illustrations of some of the presently
preferred embodiments of this invention. Therefore, it will be
appreciated that the scope of the present invention fully
encompasses other embodiments which may become obvious to those
skilled in the art, and that the scope of the present invention is
accordingly to be limited by nothing other than the appended
claims, in which reference to an element in the singular is not
intended to mean "one and only one" unless explicitly so stated,
but rather "one or more." All structural, chemical, and functional
equivalents to the elements of the above-described preferred
embodiment that are known to those of ordinary skill in the art are
expressly incorporated herein by reference and are intended to be
encompassed by the present claims. Moreover, it is not necessary
for a device or method to address each and every problem sought to
be solved by the present invention, for it to be encompassed by the
present claims. Furthermore, no element, component, or method step
in the present disclosure is intended to be dedicated to the public
regardless of whether the element, component, or method step is
explicitly recited in the claims. No claim element herein is to be
construed under the provisions of 35 U.S.C. 112, sixth paragraph,
unless the element is expressly recited using the phrase "means
for."
TABLE-US-00001 TABLE 1 Symbol XXS XS S M L Contact Diameter (mm) 5
10 20 23 55 Approx Outer D.sub.o (mm) 5 10 20 23 55 Approx Middle
D.sub.i (mm) 4 6 10 15 40 Approx Inner D.sub.c (mm) 2 2 4 5 7
TABLE-US-00002 TABLE 2 Tabulated Normalized Responses of M, S, XS
and XXS Electrodes M S Base- Base- XS XXS Time M line S line XS
Baseline XXS Baseline 0 2.32 2.04 1.89 1.5 0.261 0.24 1.12 1.04 5
2.32 2.04 1.9 1.5 0.256 0.24 1.1 1.04 10 2.38 2.04 1.92 1.5 0.259
0.24 1.07 1.04 15 2.4 2.04 1.99 1.5 0.255 0.24 1.06 1.04 20 2.39
2.04 1.93 1.5 0.248 0.24 1.05 1.04 25 2.25 2.04 1.92 1.5 0.25 0.24
1.04 1.04 30 2.21 2.04 1.88 1.5 0.248 0.24 1.04 1.04 35 2.18 2.04
1.86 1.5 0.245 0.24 1.04 1.04
* * * * *