Biomedical Engineering Reference
In-Depth Information
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Individuals
Mean for one structure over all individuals
Erosion by 1/2 voxel
Erosion by one voxel
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Surface-to-Volume Ratio
Figure 11.14:
Similarity index vs. surface-to-volume ratio. Each dot represents
one structure in one brain (418 structures in total). The average over all individ-
uals for one structure is marked by a
×
. The solid and dashed lines show the
theoretical relationship between SVR and SI for misclassification of all and half
of all surface voxel, respectively.
its surface-to-volume ratio are close to the respective means over all structures
(volume 141k pixels vs. mean 142k pixels; SVR 0.24 vs. mean 0.36). The segmen-
tation accuracy for the segmentation shown was SI
=
0.86, which is the median
SI value over all structures and all brains.
11.5.4
Comparison of Atlas Selection Strategies
The results achieved using the different atlas selection strategies outlined above
are visualized in Figs. 11.16-11.19. Each graph shows a plot of the distribu-
tion of the SI segmentation accuracies over 19 segmentations, separated by
anatomical structure. There were 19 segmentations per strategy as one out of
the 20 available bee brain images served as the fixed individual atlas for the
IND strategy. Therefore, this brain was not available as the raw image for the
remaining strategies, in order to avoid bias of the evaluation.
A comparison of all four strategies is shown in Fig. 11.20. It is easy to see from
the latter figure that the widely used IND strategy produced the least accurate
