Biomedical Engineering Reference
In-Depth Information
red circles are the cluster on the left, and green triangles are the cluster at the
top right. Again, points with similar score values are likely to have similar
spatial coordinates.
Since the differences are not found in the first two factors (but require
both the second and third), the differences in the spectra are expected to be
smaller than in the previous examples, and this is indeed the case.
Presumably, this means that the chemical differences in the tissue types
are not as extreme as in the case of GIII, indicating that the spectral differ-
ences among the spectra of GII are not that apparent.
iDC grade i
In the case of the Grade I type of the cancer, the histogram as presented
in Figure  5.42, shows two clusters that are not strongly separated. Once
again, the two clusters correspond to the left and right halves of the sample
(blue asterisks = cluster 1, at top; red circles = cluster 2, at bottom), polygonal
regions containing the clusters, and the clusters are plotted with their ( x , y )
coordinates in Figure 5.43.
Plotting x against T2 shows a smooth transition, in keeping with the poor
differentiation of the clusters and suggesting a continuous change in tissue
type. Plotting the original spectra averaged over each cluster shows the same
trend as previously seen. Plotting all of the spectra, instead of just the aver-
ages, shows that the averages are a good representation of all the spectra.
If the cluster edges are chosen to be closer together, the separation in the
spectra is not that great. This can be demonstrated by the histograms pre-
sented in Figure 5.44.
DCiS High Nuclear grade (HNg)
This sample has an unusual histogram for T1 and T2 and the three clusters
correspond to horizontal bands across the sample as shown in Figure 5.45.
× 10 -4
1
0
-1
-4
-3
-2
T1
× 10 -4
Figure 5.42
GI: clustering histogram for T1 and T2.
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