Respect for Tissue Representation Using Photoelastic Stress Analysis for Endovascular Surgery Simulation - Microsurgery: Advances, Simulations, and Applications - page 155

A vasculature model with similar morphology as shown in Fig. 4.27
was used. The reference trajectory was constructed from a set of ive
trajectories and is shown in Fig. 4.31. The robot used for catheter
manipulation was presented in [11].
The inexpert user succeeded in entering the correct branch after
six trials; the back and forth motion is shown in Fig. 4.32, where the
value of c x has local maxima at t = 0.26, t = 0.34, t = 0.52, t = 0.63
and t = 0.77 before reaching the target. At t = 0.70, the inexpert user
inserted the catheter into a branch not leading to the target and
then pulled back the catheter between t = 0.70 and t = 0.84 from
pixel (530; 157) to (339; 188), during that motion, the stress level
reached its global maximum at 12.43% of pixels with stress above
1280 mmHg. The average stress value along the trajectory is 7.31%.
During the robotic manipulation, Fig. 4.33 shows a variation of c x
corresponding to the stepping motion of the catheter insertion robot
and shows an insertion to the correct branch in the irst trial. The
average stress value along the trajectory is 6.61% and its global
maximum is 7.44%.

450 10

600

400 9

L1 L2

500

350 8

L3 L4

7

L5 Reference 300

400

6

250

300

5

200

4

150

200

L1 L2

L1 L2

3

L3 L4

L3 L4

100

L5 Reference

100 L5 Reference 2

50

1

0 0

0

0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0

0.0 0.2 0.4 0.6 0.8 1.0

Normalized Time [-] Normalized Time [-]

Normalized Time [-]

Figure 4.31 Reference trajectory construction for motion capture and
stress variables.

700

Human-X
Human-Y
Reference X
Reference Y

Reference Trajectory
Human
Morphology

650

12 Human

Reference

400

600

550

10

500

300

450

8

400

350

6

200

300

250

4

200

100 150

2

100

50

0

0

0

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 100 200 300 400 500 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

600

X-axis [px] Normalized Time [s]

Normalized Time [-]

Figure 4.32 Catheter driven by an inexperienced person: Insertion path
projection in the XY-plane compared to blood vessel morphology
and reference trajectory, catheter tip tracking in normalized
time for both axes, stress level variation in normalized time.