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

Chapter 2 Literature Review 39
Apart from the direct measurement of volume based on the defined ROI, mor-
phometric methods such as tensor-based morphometry (TBM) and voxel-based
morphometry (VBM, Ashburner and Friston, 2000, for review, see Ashburner and
Friston, 2003) evaluate the local changes in brain structures without explicitly cal-
culate the absolute volume. While the structural changes are identified in TBM
from the Jacobian of the deformation between two images, VBM compares the
concentration of gray matter (or white matter) in the local tissues voxel by voxel,
which has been used in AD studies to detect the medial temporal lobe atrophy
(e.g. Baron et al., 2001; Frisoni et al., 2002), and to measure the hippocampal
atrophy (Testa et al., 2004). Findings from morphometric MRI studies in AD and
MCI using VBM have been reviewed by Busatto et al. (2008).
Boundary shift integral (BSI, Barnes et al., 2004, 2007) is another method that
compares the baseline and the follow-up images and measures the shift in the
hippocampal boundary.
2.3.2 Shape analysis
Volume alone provides significant discrimination ability, but is inadequate to fully
describe the effect of the disease on the morphology of hippocampus. In addition
to volumetry, hippocampal shape analysis also contributed to the understanding
of the development of the disease. Regional differences between hippocampal
subfields have been found in the neurodegenerative process of AD, with more
pronounced neuron loss reported in CA1 and subiculum subfields (West et al.,
1994; Bobinski et al., 1998; Rössler et al., 2002; Mueller and Weiner, 2009; for
review see Scher et al., 2007). With the development of brain mapping techniques
such as radial atrophy mapping (Thompson et al., 2004; Frisoni et al., 2008), and
high-dimensional brain mapping (Csernansky et al., 2000; Wang et al., 2003, 2006),
findings from neuroimaging studies into AD and MCI have also corroborated the
locality of shape changes in CA1 and subiculum subfields along with global tissue
reduction (Csernansky et al., 2005; Apostolova et al., 2006; Scher et al., 2007;
Chételat et al., 2008; Qiu et al., 2009). Both shape and volume of hippocampus