Biomedical Engineering Reference
In-Depth Information
FIGURE 15.3
Trajectory and total displacement comparisons between experimental and calculated values of
bead movement for the pig brain under a 12 mm piston-induced displacement in the temporal
lobe (i.e., shown are Dx (top left), Dy (top right), Dz (bottom left), and total displacement
(bottom right)). A good correspondence is achieved when the distance between measured
displacement (X) and predicted displacement (O) is small (i.e., line connecting (X) and (O) at
each point is small).
shows a set of point-by-point comparisons of the Cartesian components of com-
puted and measured displacement vectors in the porcine brain
in vivo
. These
investigators opted to develop an experimental animal system where point
displacement vectors could be measured as a strategy for beginning the model
validation process in the neurosurgery setting. They chose to implant tem-
plates of small (1 mm) stainless steel beads through stereotactic technique in
the closed cranium and then to insert some form of displacement source to
impart a mechanical load. Figure 15.4 is a fluoroscope film illustrating a com-
pleted bead implant. Preprocedure MR scans were used to define a finite ele-
ment mesh of the pig brain for modeling purposes. Issues related to anatomical
mesh generation from high resolution preoperative scanning are discussed in
the next section. Tissue deformation and concomitant bead movement were
tracked with intraoperative CT which allowed detailed 3D maps of bead
motion to be deduced from a series of CT scans. Several different types of loads
