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

12 Chapter 1 Introduction
background to sequence design is found in the classical introduction by Haacke
et al. (1999).
1.1.3.2 Structural MR in AD
Clinical and research of structural MRI imaging marker in AD are recently re-
viewed by Frisoni et al. (2010) and McEvoy and Brewer (2010). The identification
of medial temporal lobe atrophy and especially hippocampal atrophy of particular
interest in MR studies into AD, which are well established markers of the neu-
rodegeneration process in Alzheimer’s disease. Pathologically, the development of
hippocampal atrophy is correlated with the deposition of neurofibrillary tangles
(Whitwell et al., 2008; Vemuri et al., 2008b, 2009), and neuronal counts (Bobinski
et al., 1999; Gosche et al., 2002; Jack et al., 2002). In terms of neuropsychological
measurements, the degree of atrophy is also found linked to the memory decline
(Thompson et al., 2004; Morra et al., 2009; Kovacevic et al., 2009; Walhovd et al.,
2010).
In high resolution MR images, visible changes of atrophies are observed. Visual
rating on T1-weighted MR image is one way to assess the hippocampal lobe atro-
phy (Scheltens et al., 1992; Korf et al., 2004; DeCarli et al., 2007; Duara et al.,
2008). Quantitative measurements on MR images with manual tracing or auto-
mated segmentation show a reduction of hippocampal volume by 15-30% in AD
in contrast to 10-15% in MCI (van der Flier et al., 2005; Shi et al., 2009). Lon-
gitudinally, the rates of hippocampal atrophy measured in AD are 4.66% (95%
confidence interval 3.92, 5.40) and 1.41% (0.52, 2.30) for MCI subjects (Barnes
et al., 2009a).
Apart from hippocampus, whole brain atrophy (Fox et al., 1999; Josephs et al.,
2008; Schott et al., 2008; Sluimer et al., 2008, 2010) and ventricular enlargement
(Jack et al., 2003; Thompson et al., 2004; Jack et al., 2004; Ridha et al., 2008)
also indicate the progression of the neurodegeneration. Higher rate of atrophy and
faster expansion of ventricle are present in advance of the onset of dementia.