| Volume 26 Issue 11-12 - Publication Date: 1 November- December June 2007 |
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| Assessment of Tissue Damage due to Mechanical Stresses |
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| S. De, J. Rosen, A. Dagan, B. Hannaford, BioRobotics Laboratory, Department of Bioengineering
University of Washington Box 352500, Seattle,
WA 98195-2500, USA P. Swanson, Department of Anatomic Pathology
University of Washington Box 352500, Seattle,
WA 98195-2500, USA and M. Sinanan Department of Surgery,
University of Washington Box 352500, Seattle,
WA 98195-2500, USA |
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| While there are many benefits to minimally invasive surgery (MIS),
force feedback or touch sensation is limited in the currently available
MIS tools, such as surgical robots, creating the potential for excessive
force application during surgery and unintended tissue injury.
The goal of this work was to develop a methodology with which to
identify stress magnitudes and durations that can be safely applied
with a MIS grasper to different tissues, potentially improving MIS device
design and reducing potentially adverse clinically relevant consequences.
Using the porcine model, stresses typically applied in MIS
were applied to liver, ureter and small bowel using a motorized endoscopic
grasper. Acute indicators of tissue damage including cellular
death and infiltration of inflammatory cells were measured using histological
and image analysis techniques. Finite element analysis was
used to identify approximate stress distributions experienced by the
tissues. Parameters used in these finite element models specifically
reflected the properties of liver, which served as an initial proxy for
all tissues, as stress distributions rather than absolute values were desired. Local regions predicted to have uniform stress by the computational
models were mapped to and analyzed in the tissue samples
for acute damage. Analysis of variance (ANOVA) and post-hoc analyses
were used to detect stress magnitudes and durations that caused
significantly increased tissue damage with the goal to ultimately identify
safe stress ‘thresholds’ during grasping of the studied tissues.
Preliminary data suggests a graded non-linear response between applied
stress magnitude and apoptosis in liver and small bowel as well
as neutrophil infiltration in the small bowel. The ureter appeared to
be more resistant to injury at the tested stress levels. By identifying
stress magnitudes and durations within the range of grasping loads
applied in MIS, it may be possible for researchers to create a ‘smart’
surgical robot that can guide a surgeon to manipulate tissues with
minimal resulting damage. In addition, surgical simulator design can
be improved to reflect more realistic tissue responses and evaluate
trainees’ tissue handling skills. |
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