Biomedical Engineering Reference
In-Depth Information
4.11
Complementary Image Processing for
Real-Time Analysis
To quantify tissue respect during endovascular surgery simulation, it
is desirable to measure in real time the stress within the blood vessel
model wall and its deformation and then relate those measurements
to the actual catheter tip location within the model. For that
purpose, irst it is necessary to diferentiate from the background of
photoelastic images the parts belonging to blood vessel model and
the parts belonging to the catheter and then locate the catheter tip
into the image.
4.11.1 Vision System
For the demonstration of real-time catheter trajectory analysis
including photoelastic effect, a multilayer model of a carotid artery
illed and submerged in glycerin is used. We selected the polariscope
shown in Fig. 4.24 due to the contrast quality and simpliications
enabled by the mathematic model. The polariscope equation (4.39)
simpliies to equation (4.24) if we consider
M
G
=
M
ex
. The pressure
inside the model remained below 40
mmHg during the experiment.
Vasculature
Model
o
o
White
Light
Polarizer 0
Analyzer 0
1/4 Lplate
45
1/4 Lplate
45
o
o
Figure 4.24
Polariscope for real-time analysis.
By aligning the model's principal branch axis parallel to the
X-axis of the cameras in a bi-planar vision system, the progression
of the catheter trajectory is principally perceived at the X-axis and
branch selection at Y- and Z-axes. Respecting this principle, the
cameras were aligned to the tank containing the blood vessel model.
A polariscope was placed parallel to each camera plane and having
the blood vessel model in between their quarter-wave plates. The
beams from a single light source were separated to pass through each
polariscope. Toshiba IKTF-2 cameras were used for the stereovision
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