Biomedical Engineering Reference
In-Depth Information
Fig. 3.20
Assembly of
14-sided polyhedra into an
alveolar ductal tree created by
Sznitman (2008) and
reproduced here
are predominantly hexagons and rectangles, with occasional pentagons. The alveoli
is then depicted as a cluster of 14-sided polyhedrons connected to each other by
matching faces forming a solid unit without any gaps (space-filling). In the centre is
a 14-sided polyhedron that has its faces removed and the edges become mouths of the
surrounding alveoli. Based on this model Snznitman (2008) produced an acinar tree
generation with characteristic alveolar dimension of 0.14 mm. The entire geometry
consists of 190 polyhedra for a total sub-acinar volume of
0.2 mm
3
which is
0.2 %
of the average volume of an entire acinus (Haefeli-Bleuer and Weibel 1988) and is
shown in Fig.
3.20
.
∼
∼
X-ray Tomographic Microscopy:
Scanned images of the acinar region need to be
obtained through high resolution scanners such as a synchrotron radiation-based X-
ray tomographic microscopy (SRXTM). This is because the surface area of the lung
parenchyma is extremely large (order of metres, i.e. 10
0
) in comparison with the
alveolar (order of microns, i.e. 10
−
6
). In the study by Tsuda et al. (2008) it is shown
that SRXTM can render volumes up to 10
9
m
3
μ
of lung tissue with resolution to a
m
3
. Their model was segmented using a threshold as a basis and
then region growing through an '
object connectivity analysis
'. Some smoothing was
performed and the final model is reproduced and shown here in Fig.
3.21
.
voxel size of 1.4
μ
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