Biomedical Engineering Reference
In-Depth Information
Figure 3.
T-Snake (white curve) and the marked grid nodes (spheres).
an efficient manner. Thus, we combined the advantages of a closer initialization
(through isosurfaces) and the advantages of using a topologically adaptable de-
formable model. These are the key ideas of our previous works [16, 15]. Let us
now examine some of the details.
At first, a
Local Scale Property
for the targets was supposed: given an object
O
and a point
p
O
, let
r
p
be the radius of a hyperball
B
p
that contains
p
and
lies entirely inside the object. We assume that
r
p
>
1 for all
p
∈
∈
O
. Hence, the
minimum of these radii (
r
min
) is selected.
Thus, we can use
r
min
to reduce the image's resolution without losing the
objects of interest. This idea is shown in Figure 4. In this simple example, we
have a threshold (
T<
150) that identifies the object and a CF triangulation whose
grid resolution is 10
×
10.
(a)
(b)
Figure 4.
(a) Original image and Characteristic Function. (b) Boundary approximation.
