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

Chapter 5 Quantitative shape analysis of hippocampus in AD 127
Sensitivity
0.78 0.82 0.86
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1e−04 1e−03 1e−02 1e−01 1e+00
Threshold α
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1e−04 1e−03 1e−02 1e−01 1e+00
(a) Testing set sensitivity, LR, MR (b) Testing set sensitivity, LR, MS
Sensitivity
0.55 0.65 0.75 0.85
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1e−04 1e−03 1e−02 1e−01 1e+00
Threshold α
(c) Testing set sensitivity, LS, MR
Sensitivity
Sensitivity
0.78 0.80 0.82 0.84 0.86
0.60 0.70 0.80
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1e−04 1e−03 1e−02 1e−01 1e+00
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(d) Testing set sensitivity, LS, MS
Figure 5.8: The sensitivity of the disease classification using bagged support
vector machines (SVMs) with varying thresholds in the landmark selection on
a separated testing set. Black circles: shape features from the Statistical Shape
Model (SSM) only; red circles: shape features with additional volume features.
of significant shape difference between the two groups revealed a different profile
with more localized effects mainly located in the posterior hippocampus. Because
global changes were mainly driven by the predominant effects in the CA1 and
subiculum subfields, it is not surprising that the changes independent from these
main effects reveals a different pattern.
It should be pointed out that the hippocampal subregions affected by AD were
identified by comparing the AD subpopulation with NC, which did not take into
account the association of AD and its cognitive outcome with other factors such
as age and level of education. Hippocampal atrophy has been shown to develop
during the course of normal aging (Jack et al., 1998; Malykhin et al., 2008; Chételat
et al., 2008; La Joie et al., 2010). The shape changes and variations reflect the
combined effect of aging and AD, which may limit the discrimination ability of
the shape analysis. In the future work it will be of interest to explicitly control
the effects of normal aging on the hippocampus and other variables such as years
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