Patient-Specific Vascular Modeling - Microsurgery: Advances, Simulations, and Applications - page 90

orientation and embedded it with liquid-state transparent silicone,
which solidiies into brain-like soft gel structure through addition
polymerization. Here, the physical characteristics (elastic modulus)
of the selected silicone gel are adjusted to reproduce the physical
characteristics of brain tissues (gray matter), and this material
presents good transparency too. As the relection indexes of silicone
elastomer and silicone gel take almost identical value (silicone
elastomer (nD25): 1.410, silicone gel (nD25): 1.404), no relection
and no refraction take place at its boundary and that realizes good
visibility on its body.

3.8 Reproduction of Subarachnoid Space

The cerebral arterial model reproduced with a pliant membranous
coniguration presented in the previous section enables the simulation
of a variety of medical treatments, including balloon percutaneous
transluminal angioplasty (PTA) and aneurismal clipping. Its
structure did not relect the existence of circumferential pliant tissue
that actually supports most external force exerted on the arterial
structure, making it dificult to maintain an anatomically correct
coniguration in actual use, since its low rigidity simultaneously
causes deformation against gravity. Much of the human cerebral
artery is surrounded by a vacant subarachnoid space, formed by
the wrinkles of the brain. This space contains cerebrospinal luid
and other pliant tissues that support the cerebral arterial structure
inside tissues from external loads exerted by blood low and medical
treatment. Considering this, in this section, we propose a method to
reproduce this subarachnoid space within a cube-shaped structure
proposed in the previous section. This coniguration enables the
interventionalist to simulate the deformation of cerebrovascular
disease and area of interest precisely against blood low and
surgical treatment, excluding the effects of distortion caused in non-
applicable areas.
We fabricated the vascular model reproduced with subarachnoid
space by the following procedure. First we reconstructed the three-
dimensional structure of subarachnoid space using digital slice
image obtained using MRI and then rapid-prototyped a lost-wax
mold of this structure as disassembled state. Then we placed this
mold around the vascular master mold covered by thin silicone
membrane. After this, we removed both the molds (subarachnoid