Magnetic Trackers: Robot Control and Vasculature Imaging - Microsurgery: Advances, Simulations, and Applications - page 248

The two-dimensional path reconstruction showed that the
proposed ACIS is able to distinguish between two branches in a
bifurcation and to pullback the catheter to the last bifurcation
to recover the desired trajectory in case it enters to an undesired
branch. The parameter C 3 n deine roll rotation of the catheter at
the LSM manipulator, the selection of the parameter depends on
the shape of the artery and the used catheter tip. This parameter
can be set originally based on the motion capture of the catheter
inserted by a surgeon inside the silicone arterial model. As observed
in Fig. 7.20, during trajectory reconstructions P a 1 had two different
conigurations. In the irst one, if the magnetic tracker detects the
reference point no action was taken and when the catheter was
coming back from P a 0 it indicates to LSM to twist the catheter and
change the sense of insertion of it. Therefore to reconstruct more
complex insertion paths dynamic sparse LUTs should be used. When
the objective is to correct the distorted frame of reference of the
magnetic tracker, the LUT are dense [12]. In this research, a sparse
LUT can be used since the micro-coils motion is limited by the walls
of the silicone vasculature. In robot manipulation and guidance, the
rule-base controller reacted with enough accuracy to control the
robotic systems to execute the desired tasks, since the catheter was
kept inside the ield of view of the camera and catheter insertion
trajectory was reconstructed.
The experiments presented in this chapter prove that with
an adequate detection range and a sparse LUT that relates the
coordinates collected with the magnetic tracker and the commands
to be sent to the robot, equations like 7.1-7.5 are enough to achieve
control in a restricted space for robot manipulation and guidance.
Therefore for reconstructing a catheter insertion path inside a
restricted space, such as a silicone vasculature, reference points are
needed at least at the following locations: at every bifurcation of
the vasculature, at the target to be reached and at all branches not
leading to the target. Therefore, this control method may be applied
to reconstruct insertion paths inside restricted environments, if
bifurcations of the trajectory are not closer than the cross section
diameter of the restricted space where the inserted object is
traveling. For the system guidance application, controlling the stress
produced by the catheter on the vascular model wall is desired to
ensure that the catheter stays inside the restricted space. To achieve
this, two approaches are possible: