Page 23 - Mobility Management, February 2017

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 biomed- ical 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.
The Background
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 hope- fully 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 ultra- sound 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 curva- ture 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 consis- tently showed that it is the anatomy and the individual anatom- ical 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 unbe- lievable how distinguished these differences are across individ- uals. 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 across individuals.
What we discovered is it’s a challenge to measure mechan-
ical 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 indi- viduals 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 indi- vidual 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 asym- metry 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.
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