Respect for Tissue Representation Using Photoelastic Stress Analysis for Endovascular Surgery Simulation - Microsurgery: Advances, Simulations, and Applications - page 137

variation in the normalized green light intensity with applied force,
showing that complete irst fringe was captured, and the value of
the photoelastic coeficient obtained for each sample. Their average
value is 1.284

×

10 -9 Pa -1 .

-09

1

1.50e

0.8

-09

1.40e

0.6

-09

1.30e

0.4

-09

1.20e

0.2 -09

1.10e

0

0.5 1 1.5 2 2.5 3 3.5 4

0 0.5 1 1.5 2 2.5 3 3.5 4

Applied Force (N)

Applied Force (N)

Figure 4.11 Variation of the green light intensity in urethane elastomer
membrane with the applied force, showing the irst fringe
(left). Variation of the photoelastic coeficient of NIPOLAN
5120 dyed yellow with the applied force (right).

4.7 Photoelastic Stress Analysis Error

Quantification

The difference between longitudinal and tangential stress for a
cylinder wall with inner pressure P is given by the following equation
[9]:
TT

¥
§ ¦

µ
· ¶

2 rP

D

rD
rD /

(4.28)

1 2

2 2

where the cylinder outer radius is r and its wall thickness is D/ 2. If P

> 40 mmHg for the blood vessel model, the stress on the model wall
is described by equation equation (4.28).
When a phantom is placed into the polariscope inside a glycerin
bath, stress on the model wall may be calculated using equations
(4.4, 4.22) or with equation (4.28) by measuring Re, D and r .
Photoelastic measurement system error may then be quantiied
using the deformation measurements.
P was increased within the blood vessel model using a syringe
and measured using a sensor for pressures below 200 mmHg

(Fig.4.12). For a range from 40-189 mmHg average stress in the

region of interest (ROI) was calculated using both methods for 16
samples (Fig. 4.7). Values of green were measured in ROI for each
sample.