Magnetic Trackers: Robot Control and Vasculature Imaging - Microsurgery: Advances, Simulations, and Applications - page 245

system was activated. According to the designed trajectory in M 1 ,
the 2 DOF of LSM were automatically modiied to reconstruct the
trajectories. For this experiment, the trajectory of the catheter was
only affected by C a 2 n and C a 3 n parameters. The value of the angle of
rotation, C a 3 n , was set manually to 180 ° and remained ixed during
all the experimentation.

Target

Refe rence point

0.8

40 mm

P' 4

P' 3

Coronal Axis
Sagital Axis

0.6

P' 2

0.4

0.2

0

P' 0

-0.2

P' 1

-0.4

-0.6

-0.8

Start

P' 0 P' 1 P' 2 P' 3 P' 4

Reference Points

Figure 7.19 Reference points of the planned trajectory (left) with their
respective measurement of dispersion (right).

The trajectory is designed to test the branch recognition property of
the ACIS, and to show that to ensure a proper path reconstruction,
reference points are only needed at least at the target, bifurcations,
and marking branches not leading to the target. For this case M 1
includes a target, two bifurcation, and two points marking the
branches of vasculature not leading to the target. For this trajectory,
the points P a 0 and P a 3 represent a branch not leading to the target.
They indicate to the controller to extract the catheter to the last
bifurcation. The points P a 1 and P a 2 are the bifurcations of the path.
They always indicate a rotation; if the catheter comes from the
points P a 0 or P a 3 , it indicates a change of direction of insertion too.
P a 4 indicates the target of the guidance and stopping the system.
When the catheter shaped sensor was placed in the start point of
the trajectory and the feedback loop was activated, the desired path
was reconstructed successfully. During the path reconstruction the
point P a 3 was not detected, as the rotation was executed properly
in P a 2 , leading the catheter to the target P a 4 . We can observe in Fig.
7.20 that the detection range is set to the maximum for P a 3 and P a 4 .
Therefore, a speciic detection range should be set for each point,