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

62 Chapter 3 Hippocampal segmentation using multiple atlases
The data used in the experiment of supervised atlas construction are from the
Australian Imaging, Biomarker & Lifestyle Flagship Study of Ageing (AIBL, El-
lis et al., 2010). Launched in November 2006, the AIBL study is a prospective
longitudinal study of ageing comprised of patients with AD, MCI and healthy vol-
unteers. The primary goal of AIBL is to develop and confirm a set of diagnostic
markers biomarkers and psychometrics that can be used to objectively monitor
disease progression and to develop hypotheses about diet and lifestyle factors that
might delay the onset of this disease. Successful completion of this work will en-
able the design and conduct of extensive cohort studies that may lead to clinically
proven preventative strategies for AD. Recruitment commenced in 2007 and has
been on a volunteer basis. A total of 1112 participants from Western Australia
(40%) and Victoria (60%) have been enrolled in the AIBL study. Basic inclusion
criteria for the AIBL study required that each participant be aged 60years of age
or older at the time of recruitment, English speaking and, if applicable, have stable
medications (e.g. controlled hypertension). Additionally, Alzheimer’s participants
were required to have a CDR of 0.5, 1 or 2, to meet the NINDCDS-ADRDA, ICD-
10 & DSM-IV criteria for probable or possible AD and to have a reliable informant
with contact of at least ten hours per week. About a quarter of the AIBL cohort
received imaging using MRI and PiB-PET.
The MR imaging was performed at 2 sites using a Siemens 3T Trio (∼60%) and
a Siemens 1.5T Magnetom Avanto (∼40%). The imaging protocol was defined
to follow guideline of Alzheimer’s Disease Neuroimaging Initiative (ADNI), with
the exception that a single T1W MPRage was acquired for each subject at each
timepoint (compared to 2 T1W MPRage scans in the standard ADNI protocol) and
no phantoms were acquired. From the population enrolled in the AIBL study, 210
brain MR images of 170 NC and 40 AD subjects, were segmented using the multi-
atlas based segmentation method with the IBSR images used as the initial set
of atlases. Among the segmentation results using IBSR atlases, 16 segmentations
were qualified and added to the database of atlases after the first iteration. Another
24 were added after the second iteration. Thus an atlas database of 40 segmented