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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
Chapter 3 Hippocampal segmentation using multiple atlases 63 images was built on a population of elderly subjects. The demographics of the selected atlases are shown in Table 3.1, all of which are NC subjects. 3.4.1.2 Results Table 3.1: Demographics of selected atlases IBSR Iter. 1 Iter. 2 No. of atlases 18 16 24 Male/Female 14/4 6/10 10/14 mean: 74.54 mean: 75.73 Age min: Juv. min: 63.68 min: 62.35 max: 71 max: 86.10 max: 88.26 MMSE N/A 27.81 28.88 The labels in the 18 IBSR atlases and 40 population specific atlases were propagated to the 210 AIBL images. The atlases were selected based on NMI similarity. For each query, 9 atlases were selected from IBSR atlases and atlases of elderly subjects respectively. The labels from the selected atlases were fused by major- ity voting. Two examples of probability image of hippocampus produced from IBSR atlases and atlases selected from elderly population are shown in Figure 3.4. The probability images fused by IBSR atlases and atlases of elderly population are evaluated quantitatively in terms of their entropy HP and the second order partial moment µ2 of their histograms. For the IBSR and the population specific atlases, the results fusing 9 atlases selected according to image similarity are presented in Tables 3.2 and 3.3. 3.4.1.3 Discussion The results show that, the agreement among the elderly population specific atlases is in general higher than that from IBSR, when being propagated to query images in the dataset of elderly subjects. For both NC and AD cases, the entropy is higher when probability images are fused with atlases of the IBSR than that of atlases selected from elderly population, indicating a higher randomness in the probability images produced using IBSR atlases. In terms of the second order
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UNIVERSITE DE BOURGOGNE U.F.R. SCIE
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Résumé L’objectif de cette thè
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Abstract The aim of this thesis is
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TABLE DES MATIÈRES Acknowledgement
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TABLE DES MATIÈRES xi 4.1.4.3 Spec
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LISTE DES FIGURES 1.1 Cortical atro
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144 LIST OF PUBLICATIONS using dive
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146 BIBLIOGRAPHY Alzheimer, A. (191
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148 BIBLIOGRAPHY Baillard, C., Hell
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150 BIBLIOGRAPHY of post mortem mag
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152 BIBLIOGRAPHY B. (2008). Three-d
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154 BIBLIOGRAPHY Cootes, T. F., Tay
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156 BIBLIOGRAPHY head in MR images
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158 BIBLIOGRAPHY Evans, A. C., Coll
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BIBLIOGRAPHY 161 Ghanei, A., Soltan
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BIBLIOGRAPHY 163 Heckemann, R. A.,
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BIBLIOGRAPHY 165 R. C. (2003). MRI
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BIBLIOGRAPHY 167 Konrad, C., Ukas,
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BIBLIOGRAPHY 169 Mahony, R. and Man
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BIBLIOGRAPHY 171 disease, mild cogn
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BIBLIOGRAPHY 173 Petersen, R. C., S
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BIBLIOGRAPHY 175 Rorden, C. and Bre
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BIBLIOGRAPHY 177 Shen, K., Bourgeat
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BIBLIOGRAPHY 179 Barillot, C., Hayn
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BIBLIOGRAPHY 181 Tzourio-Mazoyer, N
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BIBLIOGRAPHY 183 Vos, F. M., de Bru
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BIBLIOGRAPHY 185 Woolrich, M. W., J
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