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

Chapter 2 Literature Review 21
Figure 2.3: Delineation of hippocampus in the labelings from the Internet
Brain Segmentation Repository (IBSR). Image source: Makris et al. (2004).
The inferior medial border includes the subiculum, most of the presubiculum, and
approximately a quarter of the parasubiculum. The fimbria posterior to the com-
missure is excluded. The lateral ventricle is used as the external landmark where
the hippocampal tail terminates.
Other protocols translating the anatomical definition and description into the im-
age domain are developed to make the manual tracing of the hippocampus in-
dividual MR images operable. Although hippocampus is a complex structure
convoluted inside the medial limbic lobe, its boundary is recognizable under high
resolution MR where it borders with adjacent white matter and CSF. While its
boundary with amygdala is more difficult to distinguish. The manual delineation
of the hippocampi is usually performed on both the left and the right side of the
image, while sometimes the image is flipped such that both hippocampi traced on
the same side to avoid the laterality bias (Schott et al., 2003; Scahill et al., 2003).
Different anatomical guidelines used by various volumetric studies defining the
hippocampus on the MR image contributes to the variance among the results re-
ported, which have been reviewed by Geuze et al. (2004). An up-to-date review by
Konrad et al. (2009) surveyed 71 published protocols in neuroimaging literature,
which identified five main areas where the protocols differ:
• inclusion/exclusion of the white matter such as alveus and fimbria;
• the anterior hippocampus-amygdala border;
• the posterior border to which the hippocampal tail extends;