Patient-Specific Vascular Modeling - Microsurgery: Advances, Simulations, and Applications - page 92

3.9 Improvement of Visibility

Both the composite vascular model and the solid arterial model
presented in this chapter realize good transparency on their
bodies, but these models can cause deterioration in visibility under
atmospheric condition with speciic illuminating condition and
speciic observing direction. This visual deterioration is mainly
caused by optical reasons and is classiied into four categories
according to the location of occurrence and the type of phenomenon
causing deterioration:
1. Refraction at the external model surface: Makes the image of
arterial structure distorted and relects that image on several
outward surfaces with deviation
2. Refraction at the internal arterial surface: Distorts or magniies
the image of inserted medical tools
3. Relection at the external model surface: Deteriorates the
visibility of arterial structure and inserted medical tools
4. Relection at the internal arterial surface: Deteriorates the
visibility of inserted medical tools
As it is evident, the deterioration of visibility mainly arises from
refraction and relection taking place at both internal and external
surfaces of presented arterial model. The deteriorated visibility
caused by these factors makes it dificult to observe the inward
arterial structure and also the movement of inserted medical tools,
and consequently this makes surgical simulation rather dificult.
However, as all the above categorized factors originate in the
difference of refraction index between the presented arterial model
itself and its circumferential environment (atmosphere), these
unfavorable optical effects are eliminable with the use of optically
adjusted liquid. Figure 3.14 shows the effectiveness of this liquid.
In this case, we adopted glycerol solution (mixture of water (44%)
and glycerin (56%), which has same the relection index as silicone
elastomer; refraction index (nD25): 1.403) as that liquid. Since the
presented arterial model is made of silicone (refraction index (nD25):
1.404) too, these two material take similar refraction index for a
wide wavelength range. A salt solution and a glycerol solution are
also effective as this optically adjusted liquid; even water (refraction
index (nD20): 1.333) can be great help to improve visibility.