Docteur de l'université Automatic Segmentation and Shape Analysis ...
Docteur de l'université Automatic Segmentation and Shape Analysis ...
Docteur de l'université Automatic Segmentation and Shape Analysis ...
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20 Chapter 2 Literature Review<br />
Figure 2.2: AAL labeling overlayed on collins27. From left to right: axial,<br />
coronal, sagittal section.<br />
effect of averaging, the blurred boundary in these atlases represents the probability<br />
of structural labeling at a given coordinate in the normalized space. A single<br />
subject template collins27 from MNI with more structural <strong>de</strong>tails was created by<br />
repeated acquisitions of the same young male subject for 27 times, which were<br />
then normalized to the same space of MNI305 to produce an average image. The<br />
automated anatomical labeling (AAL, Tzourio-Mazoyer et al., 2002, see Figure 2.2)<br />
has been <strong>de</strong>veloped on the MNI single subject image, i<strong>de</strong>ntifying 45 anatomical<br />
volumes of interest in each hemisphere. In the <strong>de</strong>finition by AAL, the hippocampal<br />
region was <strong>de</strong>fined on the sagittal views as the gray matter un<strong>de</strong>r the inferior horn<br />
of the lateral ventricle. The <strong>de</strong>ntate gyrus, the uncus, <strong>and</strong> the hippocampus proper<br />
are inclu<strong>de</strong>d. The posterior boundary is limited by the parahippocampal ramus<br />
of the collateral fissure.<br />
Besi<strong>de</strong>s the st<strong>and</strong>ard labelings of AAL, the Internet Brain <strong>Segmentation</strong> Reposi-<br />
tory (IBSR) 1 also provi<strong>de</strong>s the segmented data of 18 subjects, which are labeled by<br />
trained experts into 43 individual regions including subcortical structures such as<br />
caudate, hippocampus, pallindum, putamen, thalamus, amygdala, etc. The hip-<br />
pocampal segmentations in IBSR are to be used as atlases in the preparation of this<br />
thesis. The segmentations are manually traced using intensity contour line with<br />
manual editing (Makris et al., 2004). The hippocampus-amygdala bor<strong>de</strong>r is traced<br />
in the sagittal view by drawing a sulci line in the middle of the inferior ventricle.<br />
1 Available at http://www.cma.mgh.harvard.edu/ibsr/.