Using Porous Media Theory to Determine the Coil Volume Needed to Arrest Flow in Brain Aneurysms - Porous Media: Applications in Biological Systems and Biotechnology - page 242

VELOCITY (m/sec)
TIME 3.000

VELOCITY (m/sec)
TIME 3.213

0.4358

0.05000

0.3900

0.1625

0.3300
0.2700
0.2100

0.1375
0.1125
0.0875

0.1500

0.0625

0.0900

0.0375

0.0300

0.0125

Beginning of the cycle During acceleration

VELOCITY (m/sec)
TIME 3.311

VELOCITY (m/sec)
TIME 3.481

0.6494

0.4439

0.6000
0.5000
0.4000
0.3000

0.3900
0.3300
0.2700
0.2100

0.2000

0.1500

0.1000

0.0900

0.0000

0.0300

Peak systole During deceleration

FIGURE 6.4
Temporal variation of the flow patterns within a wide-necked aneurysm in the
absence of coils. Flow from left to right.

It can be seen from Figure 6.6 that the inflow to the aneurysm sac was sig-
nificantly slowed at the aperture plane because of the presence of coils, which
occupied a small volume of the aneurysm (20%). This minimum amount of
coils is sucient to arrest flow and promote thrombosis within the sac of the
aneurysm, the usual site for rupture.

6.8 Minimum Packing Density of the
Endovascular Coil
For aneurysms at high risk of rupture, the minimum length of coil inserted
into aneurysm sac needed to arrest blood flow may be estimated from the