Docteur de l'université Automatic Segmentation and Shape Analysis ...

126 Chapter 5 Quantitative shape analysis of hippocampus in AD
Sensitivity
Sensitivity
0.73 0.75 0.77
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1e−04 1e−03 1e−02 1e−01 1e+00
Threshold α
(a) OOB sensitivity, LR, MR
0.65 0.70 0.75
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1e−04 1e−03 1e−02 1e−01 1e+00
Threshold α
(c) OOB sensitivity, LS, MR
Sensitivity
Sensitivity
0.71 0.73 0.75 0.77
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1e−04 1e−03 1e−02 1e−01 1e+00
Threshold α
(b) OOB sensitivity, LR, MS
0.65 0.70 0.75 0.80
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1e−04 1e−03 1e−02 1e−01 1e+00
Threshold α
(d) OOB sensitivity, LS, MS
Figure 5.7: The out-of-bag (OOB) estimates of sensitivity of the disease classification
using bagged support vector machines (SVMs) with varying thresholds
in the landmark selection. Black circles: shape features from the Statistical
Shape Model (SSM) only; red circles: shape features with additional volume
features.
correspondences by closest point on the separate testing set as compared to the
cross validation on training set equipped with MDL-optimized correspondence.
Therefore we opted for the closest-point as a more practical method to process the
correspondences on the testing set.
5.6.2 Identification of atrophy affected subregions
The results of the Hotelling’s T 2 test superimposed on the hippocampal surface
were compared to the maps showing the location of the different hippocampal
subfields (La Joie et al., 2010, see Figure 5.13). Regions of significant differences
between AD and NC were found mainly located in the CA1 and subiculum sub-
fields (Figure 5.2(a)), which is consistent with previous studies (Chételat et al.,
2008; Apostolova et al., 2010; Mueller et al., 2010). When the effect of volume
change was removed in SSM by similarity alignment (Figure 5.2(b)), the regions