Biomedical Engineering Reference
In-Depth Information
Then it is deduced that this control could be used to guide a
catheter through a predeined path changing the catheter's motion
with a sparse LUT. This feedback showed to be useful to reconigure
the system in a neighborhood of a point in space, but its resolution
depends on the arterial cross section radius. This can create
ambiguities if the points of the map are closer than the cross section
diameter of the artery. Therefore a limitation of the system is that the
distance between reference points of sparse LUT cannot be less than
the cross section diameter of the artery. If two references are closer
than a cross section diameter, the system will have more than one
coniguration in one point of space producing an erratic behavior
of the ACIS. In those points, the system may alternate between the
deined conigurations due to the error introduced by the magnetic
tracker.
7.4.4
One-Dimensional Path Reconstruction
A irst path reconstruction experiment was done with the purpose
to evaluate the effect of the feedback of catheter's tip position on the
linear degree of freedom of LSM. Additionally the ACIS's accuracy
to change the direction of insertion with respect to a sparse LUT
was evaluated. In this case, the sparse LUT
M
1
,
only modiies the
parameter
C
a
2
n
to change the direction of the catheter motion. For
that reason, the designed path is said to be one-dimensional. The
system was tested inside a silicone model of carotid artery and
inside a silicone model of ureter (Fig. 7.17). For the experiment
inside the vascular model, four reference points were collected
when the magnetic tracker was inserted manually into the straight
segment of the silicone model of region 3. From these references a
sparse LUT with ive vectors was constructed to obtain a trajectory
with four directional changes to be reproduced. To reconstruct those
trajectories properly, only one reference point is active at the time
and the points
P
a
2
and
P
a
4
are located in the same coordinates with
different conigurations.
The detection range
d
n
was set to 6 mm in all the reference points.
The sparse LUT was then loaded on the PC, the magnetic tracker
was placed at the start point inside the common carotid model, the
magnetic tracker console and LSM unit were initialized by the PC,
Search WWH ::
Custom Search