Medical Simulation is an important application of haptics that is emerging
rapidly. Each issue in medical simulation is challenging right from modeling
to training medical personnel.
Modeling Challenges:
Modeling soft tissue is an important issue in medical simulation because
they exibit complex material properties. They are non-linear, anisotropic,
viscoelastic and nonhomogeneous (usually layered). Moreover, soft tissues
deform considerably under the application of relatively small loads. Because
of these and many other reasons it is very difficult to obtain in vivo
material properties of living tissues. Our facility for measuring
in vivo material properties
of living tissues uses a haptic feedback device and a mechanical
stimulator.
Real time simulation of these soft-tissue is challenging because the
contact points between the tool and the tissue can occur at other than
nodal points. Cutting, for example, is a computationally expensive task
since it requires meshing and remeshing. Achieving this poses significant
obstacles in real time application, given the high rate requirement of
haptic rendering. We have developed meshless numerical
schemes for medical simulation.
Triangle is widely used as a modeling and rendering primitive in representing
continuous surfaces since it exploits coherence effectively while graphically
rendering. As the scene complexity increases, this way of exploiting coherence
becomes expensive especially when the size of the triangle is less than
that of a pixel. We use points as primitives for
modeling geometry and haptics.
Simulation Challenges:
Performing epidural injection is a clinical task that demands a high level
of skill and precision from physician. Our epidual
injection simulator provides the user with realisitic haptic feel of
interactions between the needle and vertebra or soft tissues encountered
during an actual procedure.
Minimally invasive surgery has been used in a range of procedures since
the early sixties. Unfortunately, the lack of generalized guidelines for
appropriate training, and credentialing has led to the widespread, unregulated
introduction of laparoscopy, which has resulted in numerous operative
complications. Advanced laparoscopic procedures (e.g hernia repairs, antireflux
procedures, colectomy) require significantly greater skills than those
for simple extirpative procedures (e.g cholecystectomy, splenectomy, adrenalectomy).
The goal of our Laparoscopic Simulator is to
simulate these advanced procedure.
Rendering Challenges and Techniques:
Realistic rendering of anatomical objects using traditional texture mapping
techniques is not successful because of the texture stetching problem. Visual
effects in surgical simulations such as glistening has been a challenge.
We have used environment mapping techniques for achieving visual
realism in our simulations.
High update rates of haptic rendering poses significant challenges for
medical simulations. We have used several simple
techniques to overcome some of these challenges.
Training:
Many surgeons believe that successful surgical training require highly realistic
simulation trainers, even though low fidelity simulators have been used
effectively for training in many domains. Our study aims at unravelling
the relationship between the fidelity of simulation
and training effectiveness.
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