Biomedical Engineering Reference
In-Depth Information
FIGURE 15.12
Interstitial pressure traces over time recorded during a deformation experiment.
are potentially important determinants of brain tissue mechanical response.
Studies performed by Wolfla et al.
34, 35
have shown that significant pressure
gradients can occur when the brain is subjected to large displacements.
Under conditions of acute mass expansion in the porcine brain, their inter-
stitial pressure curves exhibited a characteristic spike in interstitial pressure
corresponding to expansion followed by a period of exponential decay
between expansions, with a gradual accumulation of strain-induced gradi-
ents across the brain. These measurements are very similar to Figure 15.11b
and other data
calculations obtained in the pig brain for the types of load-
ing conditions used by Miga et al.
23
In additional pig experiments, pressure
sensors are implanted in the brain and monitored while the subject is
undergoing a temporally located load. Figure 15.12 shows the pressure
time traces measured in the pig brain at several locations in the cranium
under two successive piston displacements of 4 mm and 8 mm, respec-
tively, which mimic the behavior noted by Wolfla et al.
35
Comparable pres-
sure responses have been produced with a consolidation model approach,
although the computed absolute peak pressure levels have generally
exceeded those measured experimentally, depending on the tissue prop-
erty and cortical surface boundary condition assumptions that have been
invoked.
23
