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Not too long ago, pressure injuries were pressure ulcers or
pressure sores, and clinicians were only taught to watch for
changes in the color, texture and temperature of patients’
skin. Then came research into and understanding of deep tissue
which occur internally and can’t be observed at surface-of-the-skin levels. Now in answer to that, new studies have examined how
ultrasound technology can play a role in risk assessment — and could
shape wheelchair seating development going forward.
Interviewees for this story were Jonathan S. Akins, Ph.D.,
assistant professor, Widener University, Chester, Pa.; David M.
Brienza, Ph.D., professor and associate dean for research, School
of Health & Rehabilitation Sciences, University of Pittsburgh;
Professor Amit Gefen, Ph.D., professor, department of biomedical
engineering, Tel Aviv University; and Kara Kopplin, senior
research manager, Research and Innovation, Permobil.
While their main focal point was the study of ultrasound use in
pressure injury risk assessment, their discussion also referenced
aspects of pressure injuries that we’ve known about for some
time, as well as what risk assessment could look like in the future.
Kara Kopplin: We were very interested in being a part of research
studies around the risks of pressure injuries, with a goal toward
prevention. We’ve done quite a bit of partnership work with Dr.
Gefen, with Tel Aviv University, with MRI [Magnetic Resonance
Imaging] and the finite element models, then in the last couple
of years, with Dr. Brienza and his group as well, analyzing direct
MRI imaging with people sitting on different cushions. We know
the seated MRI can’t be used in a clinical setting, and our hope
was that something would evolve that would someday be able to
provide a patient-specific tool to assess risk of pressure injury.
So that’s where we pursued the use of ultrasound. We wanted
to see if that could be a valuable method that could be more cost
effective and more accessible to people in the future, to provide a
better assessment of risk than what is available today, and hopefully
lead to the prescription of seating systems and protocols that
will be personalized for the best individual outcomes.
Q: What Can Ultrasound Accomplish?
Mobility Management: Did the research show that ultrasound
technology was a comparable substitute for MRI?
David Brienza: Dr. Gefen has done this body of work over the
last 10 years in which he’s been able to generate an understanding
of what’s happening in the deeper tissues. What’s allowed him
to do that was being able to fine-image the geometry of the
tissue and then use the finite element modeling tool to simulate
different conditions. His work has generated the knowledge of
what parameters are important to this problem.
The important research question here really isn’t Does ultrasound
substitute for MRI? I think the better and related question
is Does ultrasound give you the critical information you need to
predict the effects that are important for determining risk, and
determining what intervention is appropriate for a particular
person in a seated situation?
We weren’t looking to see whether ultrasound did the same
thing as MRI, because it doesn’t. MRI gives you a much more
complete picture of the anatomy. But what we were interested in
is Can ultrasound measure those critical tissue thicknesses and the
critical characteristics of the bone structure, the ischial tuberosity
(IT) bone structure? Can we measure that distance, and is that
measurement equivalent to the measurement we get using the
MRI methodology? Finally, can we assess, in this case, the curvature
of the bone? If successful, we would have taken the first step
toward developing a clinically feasible method for assessing the
important parameters related to deep tissue injury risk.
Amit Gefen: Dave very accurately described the background
and the motivation. The work that we have been doing has consistently
showed that it is the anatomy and the individual anatomical
differences which are very different across individuals. It
is the anatomy that has the strongest influence on the state of
mechanical loads in tissues, particularly the peak loads in tissues.
For example, the sharpness of the bony prominences: It’s unbelievable
how distinguished these differences are across individuals.
One [person] could have a very sharp bone, and the other
could have a more blunt bone surface. Even when you look at the
same individual and you look at an MRI scan: You look at the left
bone and the right bone, and you see a difference in the curvature
of the bone, just from the left to the right side of the body. Much
like your right arm is not identical to your left arm.
So the thickness of the different tissue layers, the overall
thickness of the soft tissues, that’s important. But actually,
these anatomical features are much more important than the
stiffness properties that these tissues have, which also vary
What we discovered is it’s a challenge to measure mechanical
properties of tissues in living human beings. There are
now emerging methods that are specific for that. It’s still quite
expensive and not that accessible. What we discovered is if you
know something about internal anatomy, then the mechanical
properties are less important because the differences across individuals
in tissue mechanical properties are not as dramatic as the
differences in anatomies, that is, in internal anatomical features.
And that basically leads to what Dave said about the need to then
cost effectively capture these anatomical features of the individual
without sending people for MRI scans, which is obviously
not something that you would do outside the research lab.
Q: Why Is the Idea of Asymmetry Important?
Mobility Management: So a critical finding of your research was
that not only do the structures of the ischial tuberosities vary
from person to person, but our ITs also vary in shape within our
own bodies, meaning that our left IT could be differently shaped
than our right IT?
Jonathan Akins: I think what the study has done is confirmed
that there is this difference from side to side and this asymmetry
in this data that we collected — this particular study was
on six people, and four of them had spinal cord injuries. One
of the parameters that we published is we found there were
pretty dramatic differences in the way the tissue deformed from
side to side in a particular person. So I think the assumption
that there’s [symmetry] is not correct, especially in people with
spinal cord injuries.
Gefen: Human beings are not symmetrical to start with. But
sometimes, a condition or a comorbidity may worsen that or
make differences larger.
People have used pressure mapping a lot in the past to capture
asymmetries in posture and in the structure of the buttocks.
Some of the information you wouldn’t be able to capture with a
pressure map because the pressure map only shows you asymmetries
that present themselves on the surface of the skin, because
that’s where the measurement is taking place. Asymmetries deep
within the body — for example, an asymmetry in the left to right
ischial tuberosities, say in the sharpness or the shape of the bones
— wouldn’t necessarily manifest in a pressure mapping measurement.
Because you have all these soft tissue thicknesses that kind
of mask the information in the deep tissues. So you may have
serious differences and exposure to mechanical loads around
these bony prominences because they’re not identical (because
they’re asymmetric), but you can’t really detect that information
when you’re far away from that site, that is, when you’re
measuring quantities on the surface of the skin.
Akins: As an example of that, there are cases in this study
where we found that some people sat on muscle on one side of
their buttocks and did not sit on muscle on the other side. They
sat on adipose tissue, on fat tissue.
Gefen: Pressure mapping wouldn’t necessarily show you that.
Because the pressure mapping doesn’t know that on one side
there is muscle tissue, and on the other side, the bone is actually
covered by fat.
Q: How Do MRI & Ultrasound Differ in the
Information They Provide?
Akins: I think one thing to pull back into consideration is the
sharpness of the ischial tuberosity, and that can play into that
asymmetry. One of the interesting findings is how we were able
to use ultrasound more reliably to obtain the radius curvature
compared to our T1-weighted MRI images. We found actually
poor reliability between raters of obtaining a “good” radius
curvature. And that was due to the inability to differentiate
between cortical bone and the musculotendinous junction. We
could have used a different type of MRI image, T2 weighted, to
potentially solve that issue, but we can easily see that and measure
that structure with the ultrasound.
So from a clinical perspective, that could be something very
useful: to not only see that asymmetry of how they sit, but what is
that sharpness, that radius curvature between the two sides?
Brienza: How the tissue compresses and how the loads are
distributed varies based on posture and how the pelvis is tilted at
any particular point in time. But those anatomical features of the
bone itself are going to be constant. So if you find a person with
a very high radius of curvature, indicating a high-risk situation,
then you know to take some special precautions for that case.
Pressure mapping might not detect this risk factor.
Maybe they were leaning to their good side when you took that
pressure map. So you didn’t see that stress concentration, that pressure
concentration because the weight was distributed away from it.
Consider the bone shape as a fundamental piece of information
that’s going to help determine how the load is going to be
distributed in the tissue beneath that bone. And the other thing
that Jon said that is really important: The ultrasound is perhaps
a better methodology for measuring bone curvature because you
can’t distinguish between the muscle junction with the bone and
the bone itself in the type of MRI imaging we performed.
Q: Does Ultrasound Technology Offer Practical,
Gefen: What we should also take into account with regards to
imaging technology: MRIs are probably not going to be much
smaller than they are today. There are some miniature MRIs, but
I don’t see an MRI system going into someone’s pocket.
With ultrasound systems, there is huge potential — you can
see the technology going there, where we end up with devices
that look like pens that we can stick in our pocket. We can talk to
our cell phone using a Bluetooth connection, and we will put that
pen-like device on the [patient’s] skin, and you’ll see what’s going
on internally on the screen of your cell phone.
So looking at where technology is going and trying to extrapolate
for the future, we should consider that risk assessment
tools as we know them today are going to be totally different 10
years from now, maybe five years from now. As technologies are
able to look at deep tissues, I’m sure that ultrasound will play an
important role. And essentially, we’ll end up with risk-assessment
tools that are able to take into account anatomical features that
we’re not taking into account using existing tools.
For example, in many of the existing risk-assessment tools,
you take the nutritional status of the patient into account by
measuring the BMI [body mass index]. BMI is essentially an
anatomical feature which is rather easy to assess: You just need
to measure the [patient’s] weight and height. If you could assess,
for instance, the sharpness of the ischial tuberosities as easily as
you would measure someone’s weight or height, you could have a
critical piece of information for the risk assessment because you
know the ischial tuberosities can be as sharp as a nail or as blunt
as the bottom of a cup. If you can measure that, then you know
this individual is at higher risk for developing a deep tissue injury
because [the IT] looks like a sharp nail. That would immediately shape your overall risk assessment, and you’re currently not doing
that because you don’t have the technology for that insight into
the deep tissues.
I see a potential for nurses, for anyone who’s doing risk assessment,
to have these tools in their pockets in the next couple of
years, which will then change the risk assessment procedures
that we know and will eventually save lives.
Brienza: Include time [savings] as well, because each of these
MRI scans took about 15 to 30 minutes, and with the ultrasound
probe, we’re able to obtain that measurement in a matter of
minutes. But it’s also done at the bedside, so that’s hitting other
points: We have the patient lie down in a seated posture on a
plinth [for an ultrasound], versus having to transfer into a seated
MRI, which is challenging for people that have a spinal cord
injury. And the transportation [for an MRI] just adds hours of
time compared to minutes [to conduct an ultrasound assessment].
Gefen: It’s important to not only describe things as they are
today, but also to look into what could happen in the very near
future as we see miniaturization of these ultrasound devices. So
they will be very cheap to the point that every nurse could have
one in his or her pocket and they will do that regularly, five or 10
times a day, whenever they see a patient, whenever they suspect
that there is something going wrong. Much like in Star Trek, they
could put this device on the skin, and it will give them complete
diagnostics, or if not complete diagnostics, at least the internal
anatomy. Actually, the technology does exist today, and it’s just a
question of time until we see it commercially.
Q: How Could This New Technology Improve
the Continuum of Client Care?
Mobility Management: It sounds as if ultrasound, because the
technology is more efficient to use and particularly if miniaturization
literally places an ultrasound device into the pocket of
every acute or long-term care nurse, has the potential to greatly
expand and improve risk assessment.
Gefen: The other thing to think about is the development of a
field in engineering or computer science or in both that we call
big data. Being able to monitor, at will, anatomical or any other
type of features in the body and then comparing them to a huge
database of measurements being taken at the same time in the
same facility, or in other facilities and being stored in the cloud.
And then being able to analyze [observations of a patient] in real
time because we’ve seen that patient’s normative data — [are
current readings] deviating from normal values?
Again, that data being transmitted to the cell phone of the nurse or to her tablet, seconds or fractions of seconds after she
takes the measurements — that’s huge. It’s not only the ability to
visualize and provide the image of what’s happening in the body,
but it’s also the computer being able to tell you: That’s normal.
Brienza: The other piece to this is once you understand the
characteristics of the person and you can model it, then you can
simulate interactions with external devices, like cushions, and
start to predict how someone is going to perform when they sit on
a cushion and how the characteristics of that cushion may change
how the person is being affected and how their tissues are being
affected. We do know that tissues deform differently when people
sit on cushions with different characteristics, so we can use that
information to choose, if you will, the best cushion based on the
personal characteristics and the characteristics of the cushion.
These measurements that we’re talking about get even more
difficult when you’re talking about a loaded situation. The
ultrasound measurement we’re making now is of someone lying
on their side [with] their buttocks exposed. It gets much more
difficult when you try to take measurements while forces are
If we can parameterize the model of the person and then apply
that to a cushion, we can predict how well that cushion is going to
protect that person and their tissues from harmful deformation.
It’s a combination of general knowledge and population
with specific risk information to arrive at the
Q: How Does the Research Move Forward
Mobility Management: Given what you’ve learned, will you
continue to study these technologies and to advance what
Kopplin: We are doing MRI assessments with Dr. Brienza’s
team to further understand the differences in anatomy, how
different people’s structures are and how that translates into that
internal tissue stress and risk that Amit and his team will be
analyzing. We are advancing the research to better understand
the role that cushions, wheelchairs, positioning, and protocols
can play in ensuring the best outcomes for wheelchair users,
which is exciting.
Gefen: We are basically laying the foundations for technologies,
either building upon existing or new technologies that will
aid clinicians in doing their daily risk assessments with patients
in a world that has currently seen no technology at all in those
aspects. It’s now only based on nurses’ skills, experience, sometimes
subjective impressions that she may have when a patient
is admitted to the facility. We’re offering a thoroughly different,
revolutionary, bioengineering approach based on technology and
solid evidence that will change the world as we know it today
and as related to risk assessment. That’s a fundamental point
to emphasize. It’s not just the fact that we took ultrasound and
compared it to an MRI. That’s the technical aspect of it. The
important aspect of it is that introduced technology to a field
which is virgin in that aspect.
Brienza: We were trying to take down that barrier that was
between utilizing that knowledge that’s been generated over
10 or 15 years and applying that in the clinic. There was this
barrier that we couldn’t make the measurements. So by assessing
whether ultrasound can make those measurements, it takes that
Gefen: We translate the basic science that we have done and the
findings that were supported by sophisticated, expensive imaging
like MRI, and with ultrasound, we are translating that into the
clinic and to the bedside.