Bayesian estimation of templates in computational anatomy

Further information: Large deformation diffeomorphic metric mapping and Bayesian model of computational anatomy

Statistical shape analysis and statistical shape theory in computational anatomy (CA) is performed relative to templates, therefore it is a local theory of statistics on shape. Template estimation in computational anatomy from populations of observations is a fundamental operation ubiquitous to the discipline. Several methods for template estimation based on Bayesian probability and statistics in the random orbit model of CA have emerged for submanifolds^[1][2] and dense image volumes.^[3]

Main article: Computational anatomy

The deformable template model of shapes and forms via diffeomorphic group actions

Further information: Group actions in computational anatomy

Linear algebra is one of the central tools to modern engineering. Central to linear algebra is the notion of an orbit of vectors, with the matrices forming groups (matrices with inverses and identity) which act on the vectors. In linear algebra the equations describing the orbit elements the vectors are linear in the vectors being acted upon by the matrices. In computational anatomy the space of all shapes and forms is modeled as an orbit similar to the vectors in linear-algebra, however the groups do not act linear as the matrices do, and the shapes and forms are not additive. In computational anatomy addition is essentially replaced by the law of composition.

The central group acting CA defined on volumes in ${\displaystyle {\mathbb {R} }^{3}}$ are the diffeomorphisms ${\displaystyle {\mathcal {G}}\doteq Diff}$ which are mappings with 3-components ${\displaystyle \phi (\cdot )=(\phi _{1}(\cdot ),\phi _{2}(\cdot ),\phi _{3}(\cdot ))}$, law of composition of functions ${\displaystyle \phi \circ \phi ^{\prime }(\cdot )\doteq \phi (\phi ^{\prime }(\cdot ))}$, with inverse ${\displaystyle \phi \circ \phi ^{-1}(\cdot )=\phi (\phi ^{-1}(\cdot ))=id}$.

Groups and group are familiar to the Engineering community with the universal popularization and standardization of linear algebra as a basic model

A popular group action is on scalar images, ${\displaystyle I(x),x\in {\mathbb {R} }^{3}}$, with action on the right via the inverse.

${\displaystyle \phi \cdot I(x)=I\circ \phi ^{-1}(x),x\in {\mathbb {R} }^{3}.}$

For sub-manifolds ${\displaystyle X\subset {\mathbb {R} }^{3}\in {\mathcal {M}}}$, parametrized by a chart or immersion ${\displaystyle m(u),u\in U}$, the diffeomorphic action the flow of the position

${\displaystyle \phi \cdot m(u)\doteq \phi \circ m(u),u\in U.}$

Several group actions in computational anatomy have been defined.

Geodesic positioning via the Riemannian exponential

For the study of deformable shape in CA, a more general diffeomorphism group has been the group of choice, which is the infinite dimensional analogue. The high-dimensional diffeomorphism groups used in computational anatomy are generated via smooth flows ${\displaystyle \phi _{t},t\in [0,1]}$ which satisfy the Lagrangian and Eulerian specification of the flow fields satisfying the ordinary differential equation:

Showing the Lagrangian flow of coordinates ${\displaystyle x\in X}$ with associated vector fields ${\displaystyle v_{t},t\in [0,1]}$ satisfying ordinary differential equation ${\displaystyle {\dot {\phi }}_{t}=v_{t}(\phi _{t}),\phi _{0}=id}$.

${\displaystyle {\frac {d}{dt}}\phi _{t}=v_{t}\circ \phi _{t},\ \phi _{0}=id\$ ;}

(Lagrangian flow)

with ${\displaystyle v\doteq (v_{1},v_{2},v_{3})}$ the vector fields on ${\displaystyle {\mathbb {R} }^{3}}$ termed the Eulerian velocity of the particles at position ${\displaystyle \phi }$ of the flow. The vector fields are functions in a function space, modelled as a smooth Hilbert space with the vector fields having 1-continuous derivative . For ${\displaystyle v_{t}={\dot {\phi }}_{t}\circ \phi _{t}^{-1},t\in [0,1]}$, with the inverse for the flow given by

${\displaystyle {\frac {d}{dt}}\phi _{t}^{-1}=-(D\phi _{t}^{-1})v_{t},\ \phi _{0}^{-1}=id\ ,}$

(Eulerianflow)

and the ${\displaystyle 3\times 3}$ Jacobian matrix for flows in ${\displaystyle \mathbb {R} ^{3}}$ given as ${\displaystyle \ D\phi \doteq \left({\frac {\partial \phi _{i}}{\partial x_{j}}}\right).}$

Flows were first introduced^[4][5] for large deformations in image matching; ${\displaystyle {\dot {\phi }}_{t}(x)}$ is the instantaneous velocity of particle ${\displaystyle x}$ at time ${\displaystyle t}$. with the vector fields termed the Eulerian velocity of the particles at position of the flow. The modelling approach used in CA enforces a continuous differentiability condition on the vector fields by modelling the space of vector fields ${\displaystyle (V,\|\cdot \|_{V})}$ as a reproducing kernel Hilbert space (RKHS), with the norm defined by a 1-1, differential operator${\displaystyle A:V\rightarrow V^{*}}$, Green's inverse ${\displaystyle K=A^{-1}}$. The norm according to ${\displaystyle \|v\|_{V}^{2}\doteq \int _{X}Av\cdot vdx,v\in V,}$ where for ${\displaystyle \sigma (v)\doteq Av\in V^{*}}$ a generalized function or distribution, then ${\displaystyle (\sigma \mid w)\doteq \int _{{\mathbb {R} }^{3}}\sum _{i}w_{i}(x)\sigma _{i}(dx)}$. Since ${\displaystyle A}$ is a differential operator, finiteness of the norm-square ${\displaystyle \int _{X}Av\cdot vdx<\infty }$ includes derivatives from the differential operator implying smoothness of the vector fields.

To ensure smooth flows of diffeomorphisms with inverse, the vector fields ${\displaystyle {\mathbb {R} }^{3}}$ must be at least 1-time continuously differentiable in space^[6][7] which are modelled as elements of the Hilbert space ${\displaystyle (V,\|\cdot \|_{V})}$ using the Sobolev embedding theorems so that each element ${\displaystyle v_{i}\in H_{0}^{3},i=1,2,3,}$ has 3-square-integrable derivatives. Thus ${\displaystyle (V,\|\cdot \|_{V})}$ embed smoothly in 1-time continuously differentiable functions.^[6][7] The diffeomorphism group are flows with vector fields absolutely integrable in Sobolev norm:

${\displaystyle Diff_{V}\doteq \{\varphi =\phi _{1}:{\dot {\phi }}_{t}=v_{t}\circ \phi _{t},\phi _{0}=id,\int _{0}^{1}\|v_{t}\|_{V}\,dt<\infty \}\ .}$

(Diffeomorphism Group)

The Bayes model of computational anatomy

The central statistical model of computational anatomy in the context of medical imaging is the source-channel model of Shannon theory;^[8][9][10] the source is the deformable template of images ${\displaystyle I\in {\mathcal {I}}}$, the channel outputs are the imaging sensors with observables ${\displaystyle I^{D}\in {\mathcal {I}}^{\mathcal {D}}}$ . The variation in the anatomical configurations are modelled separately from the Medical imaging modalities Computed Axial Tomography machine, MRI machine, PET machine, and others. The Bayes theory models the prior on the source of images ${\displaystyle \pi _{\mathcal {I}}(\cdot )}$ on ${\displaystyle I\in {\mathcal {I}}}$, and the conditional density on the observable imagery ${\displaystyle p(\cdot |I)\ {\text{on}}\ I^{D}\in {\mathcal {I}}^{\mathcal {D}}}$, conditioned on ${\displaystyle I\in {\mathcal {I}}}$. For images with diffeomorphism group action ${\displaystyle I\doteq \phi \cdot I_{\mathrm {temp} },\phi \in Diff_{V}}$, then the prior on the group ${\displaystyle \pi _{Diff_{V}}(\cdot )}$ induces the prior on images ${\displaystyle \pi _{\mathcal {I}}(\cdot )}$, written as densities the log-posterior takes the form

${\displaystyle \log p(\phi \cdot I\mid I^{D})\simeq \log p(I^{D}\mid \phi \cdot I)+\log \pi _{\operatorname {Diff} _{V}}(\phi )\ .}$

Maximum a posteriori estimation (MAP) estimation is central to modern statistical theory. Parameters of interest ${\displaystyle \theta \in \Theta }$ take many forms including (i) disease type such as neurodegenerative or neurodevelopmental diseases, (ii) structure type such as cortical or subcortical structures in problems associated to segmentation of images, and (iii) template reconstruction from populations. Given the observed image ${\displaystyle I^{D}}$, MAP estimation maximizes the posterior:

${\displaystyle {\hat {\theta }}\doteq \arg \max _{\theta \in \Theta }\log p(\theta \mid I^{D}).}$

Shown are shape templates of amygdala, hippocampus, and ventricle generated from 754 ADNI samples` Top panel denotes the localized surface area group differences between normal aging and Alzheimer disease (positive represents atrophy in Alzheimer whereas negative suggests expansion). Bottom panel denotes the group differences in the annualized rates of change in the localized surface areas (positive represents faster atrophy rates (or slower expansion rates) in Alzheimer whereas negative suggests faster expansion rates (or slower atrophy rates) in Alzheimer); taken from Tang et al.^[11][12][13]

This requires computation of the conditional probabilities ${\displaystyle p(\theta \mid I^{D})={\frac {p(I^{D},\theta )}{p(I^{D})}}}$. The multiple atlas orbit model randomizes over the denumerable set of atlases ${\displaystyle \{I_{a},a\in {\mathcal {A}}\}}$. The model on images in the orbit take the form of a multi-modal mixture distribution

${\displaystyle p(I^{D},\theta )=\textstyle \sum _{a\in {\mathcal {A}}}p(I^{D},\theta \mid I_{a})\pi _{\mathcal {A}}(a)\ .}$

Surface templates for computational neuroanatomy and subcortical structures

The study of sub-cortical neuroanatomy has been the focus of many studies. Since the original publications by Csernansky and colleagues of hippocampal change in Schizophrenia,^{[14][15][16][17]} Alzheimer's disease,^[18][19][20] and Depression,^[21][22] many neuroanatomical shape statistical studies have now been completed using templates built from all of the subcortical structures for depression,^[23] Alzheimer's,^{[11][12][24][25][26][27]} Bipolar disorder, ADHD,^[28] autism,^[29] and Huntington's Disease.^[30][31] Templates were generated using Bayesian template estimation data back to Ma, Younes and Miller.^[32]

Shown in the accompanying Figure is an example of subcortical structure templates generated from T1-weighted magnetic resonance imagery by Tang et al.^[11][12][13] for the study of Alzheimer's disease in the ADNI population of subjects.

Surface estimation in cardiac computational anatomy

Showing population atlases identifying regional differences in radial thickness at end-systolic cardiac phase between patients with hypertrophic cardiomyopathy (left) and hypertensive heart disease (right). Gray mesh shows the common surface template to the population, with the color map representing basilar septal and anterior epicardial wall with larger radial thickness in patients with hypertrophic cardiomyopathy vs. hypertensive heart disease.^[33]

Numerous studies have now been done on cardiac hypertrophy and the role of the structural integraties in the functional mechanics of the heart. Siamak Ardekani has been working on populations of Cardiac anatomies reconstructing atlas coordinate systems from populations.^[34][35][36] The figure on the right shows the computational cardiac anatomy method being used to identify regional differences in radial thickness at end-systolic cardiac phase between patients with hypertrophic cardiomyopathy (left) and hypertensive heart disease (right). Color map that is placed on a common surface template (gray mesh) represents region ( basilar septal and the anterior epicardial wall) that has on average significantly larger radial thickness in patients with hypertrophic cardiomyopathy vs. hypertensive heart disease (reference below).^[33]

MAP Estimation of volume templates from populations and the EM algorithm

Generating templates empirically from populations is a fundamental operation ubiquitous to the discipline. Several methods based on Bayesian statistics have emerged for submanifolds and dense image volumes. For the dense image volume case, given the observable ${\displaystyle I^{D_{1}},I^{D_{2}},\dots }$ the problem is to estimate the template in the orbit of dense images ${\displaystyle I\in {\mathcal {I}}}$. Ma's procedure takes an initial hypertemplate ${\displaystyle I_{0}\in {\mathcal {I}}}$ as the starting point, and models the template in the orbit under the unknown to be estimated diffeomorphism ${\displaystyle I\doteq \phi _{0}\cdot I_{0}}$, with the parameters to be estimated the log-coordinates ${\displaystyle \theta \doteq v_{0}}$ determining the geodesic mapping of the hyper-template ${\displaystyle \mathrm {Exp} _{\mathrm {id} }(v_{0})\cdot I_{0}=I\in {\mathcal {I}}}$.

In the Bayesian random orbit model of computational anatomy the observed MRI images ${\displaystyle I^{D_{i}}}$ are modelled as a conditionally Gaussian random field with mean field ${\displaystyle \phi _{i}\cdot I}$, with ${\displaystyle \phi _{i}}$ a random unknown transformation of the template. The MAP estimation problem is to estimate the unknown template ${\displaystyle I\in {\mathcal {I}}}$ given the observed MRI images.

Ma's procedure for dense imagery takes an initial hypertemplate ${\displaystyle I_{0}\in {\mathcal {I}}}$ as the starting point, and models the template in the orbit under the unknown to be estimated diffeomorphism ${\displaystyle I\doteq \phi _{0}\cdot I_{0}}$. The observables are modelled as conditional random fields, ${\displaystyle I^{D_{i}}}$ a conditional-Gaussian random field with mean field ${\displaystyle \phi _{i}\cdot I\doteq \phi _{i}\cdot \phi _{0}\cdot I_{0}}$. The unknown variable to be estimated explicitly by MAP is the mapping of the hyper-template ${\displaystyle \phi _{0}}$, with the other mappings considered as nuisance or hidden variables which are integrated out via the Bayes procedure. This is accomplished using the expectation–maximization (EM) algorithm.

The orbit-model is exploited by associating the unknown to be estimated flows to their log-coordinates ${\displaystyle v_{i},i=1,\dots }$ via the Riemannian geodesic log and exponential for computational anatomy the initial vector field in the tangent space at the identity so that ${\displaystyle \mathrm {Exp} _{\mathrm {id} }(v_{i})\doteq \phi _{i}}$, with ${\displaystyle \mathrm {Exp} _{\mathrm {id} }(v_{0})}$ the mapping of the hyper-template. The MAP estimation problem becomes

${\displaystyle \max _{v_{0}}p(I^{D},\theta =v_{0})=\int p(I^{D},\theta =v_{0}\mid v_{1},v_{2},\dots )\pi (v_{1},v_{2},\dots )\,dv}$

The EM algorithm takes as complete data the vector-field coordinates parameterizing the mapping, ${\displaystyle v_{i},i=1,\dots }$ and compute iteratively the conditional-expectation

${\displaystyle {\begin{matrix}Q(\theta =v_{0};\theta ^{\text{old}}=v_{0}^{\text{old}})&=-E(\log p(I^{D},\theta =v_{0}\mid v_{1},v_{2},\dots )|I^{D},\theta ^{\text{old}})\\&=-\|({\bar {I}}^{\text{old}}-I_{0}\circ \mathrm {Exp} _{\mathrm {id} }(v_{0})^{-1}){\sqrt {\beta ^{\text{old}}}}\|^{2}-\|v_{0}\|_{V}^{2}\end{matrix}}}$

• Compute new template maximizing Q-function, setting ${\displaystyle \theta ^{\text{new}}\doteq v_{0}^{\text{new}}=\arg \max _{\theta =v_{0}}Q(\theta$ ;\theta ^{\text{old}}=v_{0}^{\text{old}})=-\|({\bar {I}}^{\text{old}}-I_{0}\circ \mathrm {Exp} _{\mathrm {id} }(v_{0})^{-1}){\sqrt {\beta ^{\text{old}}}}\|^{2}-\|v_{0}\|_{V}^{2}}
• Compute the mode-approximation for the expectation updating the expected-values for the mode values:

${\displaystyle v_{i}^{\text{new}}=\arg \max _{v:{\dot {\phi }}=v\circ \phi }-\int _{0}^{1}\|v_{t}\|_{V}^{2}\,dt-\|I^{D_{i}}-I_{0}\circ \mathrm {Exp} _{\mathrm {id} }(v_{0}^{\text{old}})^{-1}\circ \mathrm {Exp} _{\mathrm {id} }(v)^{-1}\|^{2}.i=1,2,\dots }$

${\displaystyle \beta ^{\text{new}}(x)=\sum _{i=1}^{n}|D\mathrm {Exp} _{\mathrm {id} }(v_{i}^{\text{new}})(x)|,{\text{ with }}{\bar {I}}^{\text{new}}(x)={\frac {\sum _{i=1}^{n}I^{D_{i}}\circ \mathrm {Exp} _{\mathrm {id} }(v_{i}^{\text{new}})|D\mathrm {Exp} _{\mathrm {id} }(v_{i}^{\text{new}})(x)|}{\beta ^{\text{old}}(x)}}}$

References

1. Ma, Jun; Miller, Michael I.; Younes, Laurent (2010-01-01). "A Bayesian Generative Model for Surface Template Estimation". International Journal of Biomedical Imaging. 2010: 1–14. doi:10.1155/2010/974957. ISSN 1687-4188. PMC 2946602. PMID 20885934.
2. Qiu, Anqi; Brown, Timothy; Fischl, Bruce; Ma, Jun; Miller, Michael I. (2010-06-01). "Atlas Generation for Subcortical and Ventricular Structures with its Applications in Shape Analysis". IEEE Transactions on Image Processing. 19 (6): 1539–1547. Bibcode:2010ITIP...19.1539Q. doi:10.1109/TIP.2010.2042099. ISSN 1057-7149. PMC 2909363. PMID 20129863.
3. Ma, Jun; Miller, Michael I.; Trouvé, Alain; Younes, Laurent (2008-08-01). "Bayesian Template Estimation in Computational Anatomy". NeuroImage. 42 (1): 252–261. doi:10.1016/j.neuroimage.2008.03.056. ISSN 1053-8119. PMC 2602958. PMID 18514544.
4. GE Christensen, RD Rabbitt, MI Miller, Deformable templates using large deformation kinematics, IEEE Trans Image Process. 1996;5(10):1435-47.
5. GE Christensen, SC Joshi, MI Miller, Volumetric transformation of brain anatomy IEEE Transactions on Medical Imaging,1997.
6. P. Dupuis, U. Grenander, M.I. Miller, Existence of Solutions on Flows of Diffeomorphisms, Quarterly of Applied Math, 1997.
7. A. Trouvé. Action de groupe de dimension infinie et reconnaissance de formes. C R Acad Sci Paris Sér I Math, 321(8):1031– 1034, 1995.
8. Miller, Michael; Banerjee, Ayananshu; Christensen, Gary; Joshi, Sarang; Khaneja, Navin; Grenander, Ulf; Matejic, Larissa (1997-06-01). "Statistical methods in computational anatomy". Statistical Methods in Medical Research. 6 (3): 267–299. doi:10.1177/096228029700600305. ISSN 0962-2802. PMID 9339500. S2CID 35247542.
9. U. Grenander and M. I. Miller (2007-02-08). Pattern Theory: From Representation to Inference. Oxford University Press. ISBN 978-0-19-929706-1.
10. M. I. Miller and S. Mori and X. Tang and D. Tward and Y. Zhang (2015-02-14). Bayesian Multiple Atlas Deformable Templates. Brain Mapping: An Encyclopedic Reference. Academic Press. ISBN 978-0-12-397316-0.
11. Tang, Xiaoying; Holland, Dominic; Dale, Anders M.; Younes, Laurent; Miller, Michael I. (2015-01-01). "Baseline Shape Diffeomorphometry Patterns of Subcortical and Ventricular Structures in Predicting Conversion of Mild Cognitive Impairment to Alzheimer's Disease". Journal of Alzheimer's Disease. 44 (2): 599–611. doi:10.3233/JAD-141605. ISSN 1387-2877. PMC 4474004. PMID 25318546.
12. Tang, Xiaoying; Holland, Dominic; Dale, Anders M.; Younes, Laurent; Miller, Michael I.; for the Alzheimer's Disease Neuroimaging Initiative (2015-06-01). "The diffeomorphometry of regional shape change rates and its relevance to cognitive deterioration in mild cognitive impairment and Alzheimer's disease". Human Brain Mapping. 36 (6): 2093–2117. doi:10.1002/hbm.22758. ISSN 1097-0193. PMC 4474005. PMID 25644981.
13. Tang, Xiaoying; Holland, Dominic; Dale, Anders M.; Miller, Michael I.; Alzheimer's Disease Neuroimaging Initiative (2015-01-01). "APOE Affects the Volume and Shape of the Amygdala and the Hippocampus in Mild Cognitive Impairment and Alzheimer's Disease: Age Matters". Journal of Alzheimer's Disease. 47 (3): 645–660. doi:10.3233/JAD-150262. ISSN 1875-8908. PMC 5479937. PMID 26401700.
14. Csernansky, John G.; Joshi, Sarang; Wang, Lei; Haller, John W.; Gado, Mokhtar; Miller, J. Philip; Grenander, Ulf; Miller, Michael I. (1998-09-15). "Hippocampal morphometry in schizophrenia by high dimensional brain mapping". Proceedings of the National Academy of Sciences of the United States of America. 95 (19): 11406–11411. Bibcode:1998PNAS...9511406C. doi:10.1073/pnas.95.19.11406. ISSN 0027-8424. PMC 21655. PMID 9736749.
15. Csernansky, John G.; Wang, Lei; Jones, Donald; Rastogi-Cruz, Devna; Posener, Joel A.; Heydebrand, Gitry; Miller, J. Philip; Miller, Michael I. (2002-12-01). "Hippocampal deformities in schizophrenia characterized by high dimensional brain mapping". The American Journal of Psychiatry. 159 (12): 2000–2006. doi:10.1176/appi.ajp.159.12.2000. ISSN 0002-953X. PMID 12450948. S2CID 14924093.
16. Wang, L.; Joshi, S. C.; Miller, M. I.; Csernansky, J. G. (2001-09-01). "Statistical analysis of hippocampal asymmetry in schizophrenia". NeuroImage. 14 (3): 531–545. doi:10.1006/nimg.2001.0830. ISSN 1053-8119. PMID 11506528. S2CID 16573767.
17. Csernansky, John G.; Schindler, Mathew K.; Splinter, N. Reagan; Wang, Lei; Gado, Mohktar; Selemon, Lynn D.; Rastogi-Cruz, Devna; Posener, Joel A.; Thompson, Paul A. (2004-05-01). "Abnormalities of thalamic volume and shape in schizophrenia". The American Journal of Psychiatry. 161 (5): 896–902. doi:10.1176/appi.ajp.161.5.896. ISSN 0002-953X. PMID 15121656.
18. Csernansky, J. G.; Wang, L.; Swank, J.; Miller, J. P.; Gado, M.; McKeel, D.; Miller, M. I.; Morris, J. C. (2005-04-15). "Preclinical detection of Alzheimer's disease: hippocampal shape and volume predict dementia onset in the elderly". NeuroImage. 25 (3): 783–792. doi:10.1016/j.neuroimage.2004.12.036. ISSN 1053-8119. PMID 15808979. S2CID 207164390.
19. Wang, Lei; Miller, J. Philp; Gado, Mokhtar H.; McKeel, Daniel W.; Rothermich, Marcus; Miller, Michael I.; Morris, John C.; Csernansky, John G. (2006-03-01). "Abnormalities of hippocampal surface structure in very mild dementia of the Alzheimer type". NeuroImage. 30 (1): 52–60. doi:10.1016/j.neuroimage.2005.09.017. ISSN 1053-8119. PMC 2853193. PMID 16243546.
20. Wang, Lei; Swank, Jeffrey S.; Glick, Irena E.; Gado, Mokhtar H.; Miller, Michael I.; Morris, John C.; Csernansky, John G. (2003-10-01). "Changes in hippocampal volume and shape across time distinguish dementia of the Alzheimer type from healthy aging". NeuroImage. 20 (2): 667–682. doi:10.1016/S1053-8119(03)00361-6. ISSN 1053-8119. PMID 14568443. S2CID 21246081.
21. Posener, Joel A.; Wang, Lei; Price, Joseph L.; Gado, Mokhtar H.; Province, Michael A.; Miller, Michael I.; Babb, Casey M.; Csernansky, John G. (2003-01-01). "High-dimensional mapping of the hippocampus in depression". The American Journal of Psychiatry. 160 (1): 83–89. doi:10.1176/appi.ajp.160.1.83. ISSN 0002-953X. PMID 12505805. S2CID 12131077.
22. Munn, Melissa A.; Alexopoulos, Jim; Nishino, Tomoyuki; Babb, Casey M.; Flake, Lisa A.; Singer, Tisha; Ratnanather, J. Tilak; Huang, Hongyan; Todd, Richard D. (2007-09-01). "Amygdala Volume Analysis in Female Twins with Major Depression". Biological Psychiatry. 62 (5): 415–422. doi:10.1016/j.biopsych.2006.11.031. ISSN 0006-3223. PMC 2904677. PMID 17511971.
23. "Amygdala and Hippocampal in ADHD: Volumetric and Morphometric Analysis and Relation to Mood Symptoms". ResearchGate. Retrieved 2016-03-22.
24. Qiu, Anqi; Fennema-Notestine, Christine; Dale, Anders M.; Miller, Michael I. (2009-04-15). "Regional shape abnormalities in mild cognitive impairment and Alzheimer's disease". NeuroImage. 45 (3): 656–661. doi:10.1016/j.neuroimage.2009.01.013. ISSN 1053-8119. PMC 2847795. PMID 19280688.
25. Qiu, Anqi; Younes, Laurent; Miller, Michael I.; Csernansky, John G. (2008-03-01). "Parallel Transport in Diffeomorphisms Distinguishes the Time-Dependent Pattern of Hippocampal Surface Deformation due to Healthy Aging and the Dementia of the Alzheimer's Type". NeuroImage. 40 (1): 68–76. doi:10.1016/j.neuroimage.2007.11.041. ISSN 1053-8119. PMC 3517912. PMID 18249009.
26. Miller, Michael I.; Younes, Laurent; Ratnanather, J. Tilak; Brown, Timothy; Reigel, Tommy; Trinh, Huong; Tang, Xiaoying; Barker, Peter; Mori, Susumu (2012-10-01). "Amygdala Atrophy in MCI/Alzheimer's Disease in the BIOCARD cohort based on Diffeomorphic Morphometry". Medical Image Computing and Computer-Assisted Intervention. 2012: 155–166. PMC 4063307. PMID 24955432.
27. Miller, Michael I.; Ratnanather, J. Tilak; Tward, Daniel J.; Brown, Timothy; Lee, David S.; Ketcha, Michael; Mori, Kanami; Wang, Mei-Cheng; Mori, Susumu (2015-01-01). "Network neurodegeneration in Alzheimer's disease via MRI based shape diffeomorphometry and high-field atlasing". Frontiers in Bioengineering and Biotechnology. 3: 54. doi:10.3389/fbioe.2015.00054. PMC 4515983. PMID 26284236.
28. Qiu, Anqi; Crocetti, Deana; Adler, Marcy; Mahone, E. Mark; Denckla, Martha B.; Miller, Michael I.; Mostofsky, Stewart H. (2009-01-01). "Basal Ganglia Volume and Shape in Children With Attention Deficit Hyperactivity Disorder". The American Journal of Psychiatry. 166 (1): 74–82. doi:10.1176/appi.ajp.2008.08030426. ISSN 0002-953X. PMC 2890266. PMID 19015232.
29. Qiu, A.; Adler, M.; Crocetti, D.; Miller, M. I.; Mostofsky, S. H. (2010). "Basal Ganglia Shapes Predict Social, Communication, and Motor Dysfunctions in Boys With Autism Spectrum Disorder - Journal of the American Academy of Child & Adolescent Psychiatry". Journal of the American Academy of Child and Adolescent Psychiatry. 49 (6): 539–51, 551.e1–4. doi:10.1016/j.jaac.2010.02.012. PMID 20494264. Retrieved 2016-03-22.
30. Younes, Laurent; Ratnanather, J. Tilak; Brown, Timothy; Aylward, Elizabeth; Nopoulos, Peg; Johnson, Hans; Magnotta, Vincent A.; Paulsen, Jane S.; Margolis, Russell L. (2014-03-01). "Regionally selective atrophy of subcortical structures in prodromal HD as revealed by statistical shape analysis". Human Brain Mapping. 35 (3): 792–809. doi:10.1002/hbm.22214. ISSN 1097-0193. PMC 3715588. PMID 23281100.
31. Frieda van den Noort; Frieda van den Noort; Andreia Faria; Tilak Ratnanather; Christopher Ross; Susumu Mori; Laurent Younes; Michael Miller (2014-07-18). Anatomical connectivity in prodromal Huntington Disease. F1000Research (Poster).
32. Ma, Jun; Miller, Michael I.; Younes, Laurent (2010-01-01). "A Bayesian Generative Model for Surface Template Estimation". International Journal of Biomedical Imaging. 2010: 1–14. doi:10.1155/2010/974957. ISSN 1687-4188. PMC 2946602. PMID 20885934.
33. Ardekani, Siamak; Jain, Saurabh; Sanzi, Alianna; Corona-Villalobos, Celia P.; Abraham, Theodore P.; Abraham, M. Roselle; Zimmerman, Stefan L.; Wu, Katherine C.; Winslow, Raimond L.; Miller, Michael I.; Younes, Laurent (April 2016). "Shape analysis of hypertrophic and hypertensive heart disease using MRI-based 3D surface models of left ventricular geometry". Medical Image Analysis. 29: 12–23. doi:10.1016/j.media.2015.11.004. PMC 4850908. PMID 26766206.
34. Ardekani, Siamak; Weiss, Robert G.; Lardo, Albert C.; George, Richard T.; Lima, Joao A. C.; Wu, Katherine C.; Miller, Michael I.; Winslow, Raimond L.; Younes, Laurent (2009-06-01). "Computational method for identifying and quantifying shape features of human left ventricular remodeling". Annals of Biomedical Engineering. 37 (6): 1043–1054. doi:10.1007/s10439-009-9677-2. ISSN 1573-9686. PMC 2819012. PMID 19322659.
35. Steinert-Threlkeld, Shane; Ardekani, Siamak; Mejino, Jose L. V.; Detwiler, Landon Todd; Brinkley, James F.; Halle, Michael; Kikinis, Ron; Winslow, Raimond L.; Miller, Michael I. (2012-06-01). "Ontological labels for automated location of anatomical shape differences". Journal of Biomedical Informatics. 45 (3): 522–527. doi:10.1016/j.jbi.2012.02.013. ISSN 1532-0480. PMC 3371096. PMID 22490168.
36. Ardekani, Siamak; Gunter, Geoffrey; Jain, Saurabh; Weiss, Robert G.; Miller, Michael I.; Younes, Laurent (2014). "Estimating dense cardiac 3D motion using sparse 2D tagged MRI cross-sections". 2014 36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. Vol. 2014. pp. 5101–5104. doi:10.1109/EMBC.2014.6944772. ISBN 978-1-4244-7929-0. ISSN 1557-170X. PMC 4474039. PMID 25571140.