Biomedical Engineering Reference
In-Depth Information
Table 8.2: Maximum in-plane to out-of-plane sampling ratios of nonuniform
input datasets, and parameters for the two level set speed terms defined in
Eqs. (8.6) and (8.10)
Model
Origin
Ratio
α
β
Griffin
Laser scan
6/10:1
1.0
0.5
Mouse
MR scan
10:1
1.0
0.5
Zucchini
MR scan
10:1
1.0
0.5
8.4.2 Multiple Volume Results
We have applied our segmentation method to several multiscan nonuniform
datasets to produce high-resolution level set models. The parameters used for
these segmentations are listed in Table 8.2.
α
and
β
are weights that the user
adjusts to balance attraction to edges with curvature-based smoothing during
the level set deformation process.
8.4.2.1 Griffin Dataset
The griffin dataset was created with a volumetric laser scan reconstruction algo-
rithm [49]. This algorithm creates a high-resolution volumetric representation
of an object by merging multiple depth maps produced via a laser scan. The
original griffin dataset has a resolution of 312
×
294
×
144. We have extracted
two nonuniform datasets from this high-resolution representation by copying
every sixth plane of data in the
X
direction and every tenth plane in the
Y
direc-
tion. The two derived nonuniform griffin datasets have the following resolution:
52
×
294
×
144 and 312
×
30
×
144. Isosurfaces have been extracted from these
datasets, appropriately scaled in the low-resolution direction, and are presented
in the first two images in Fig. 8.9 (top). Each low-resolution scan inadequately
captures some important geometric feature of the griffin. We have performed a
reconstruction from the undersampled nonuniform scans to produce the result
in Fig. 8.9 (top). The method produces a high-resolution (312
×
294
×
144) level
set model that contains all of the significant features of the original scan.
8.4.2.2 Mouse Embryo Dataset
The first three scans in Fig. 8.9 (bottom) are derived from a high-resolution MR
scan of a mouse embryo. They are subsampled versions of a 256
×
128
×
128
