Biomedical Engineering Reference
In-Depth Information
evolved at a time. Thus a method which generates only the connected compo-
nent being evolved—that is, the PL generation algorithm—is interesting.
7.5 Reconstruction Method
Following the above discussion, we proposed in [22, 63] a segmentation/surface
reconstruction method that is based on the following steps: (1) extract region-
based statistics; (2) coarser image resolution; (3) define the
object characteristic
function
; (4) PL manifold extraction by the tetra-cubes; (5) if needed, increase
the resolution, return to step (3); and (6) apply T-surfaces model.
It is important to highlight that T-surfaces model can deal naturally with the
self-intersections that may happen during the evolution of the surfaces obtained
by step (4). This is an important advantage of T-surfaces.
Among the surfaces extracted in step (4), there may be open surfaces which
start and end in the image frontiers and small surfaces corresponding to arti-
facts or noise in the background. The former is discarded by a simple auto-
matic inspection. To discard the latter, we need a set of predefined features
(volume, surface area, etc.) and corresponding lower bounds. For instance, we
can set the volume lower bound as 8(
r
)
3
, where
r
is the dimension of the grid
cells.
Besides, some polygonal surfaces may contain more than one object of inter-
est (see Fig. 7.9). Now, we can use upper bounds for the features. These upper
bounds are application dependent (anatomical elements can be used).
(a)
(b)
Figure 7.9: (a) PL manifolds for resolution 3
×
3. ( b) Result with the highest
(image) resolution.
