Transcript ICOS03_Gerig_hippo - University of North Carolina at Chapel Hill

METHODS
Segmentation of hippocampal structures
• IRIS: Tool for interactive
image
segmentation.
• Manual painting in orthogonal
sections.
• 2D graphical overlay and 3D
reconstruction.
• 2D/3D cursor interaction between
cut-planes and 3D display.
• Hippocampus: Intra-rater Reliability:
0.95/0.92 Software available online:
http://midag.cs.unc.edu
Age and treatment related local
hippocampal changes in
schizophrenia explained by a novel
shape analysis method
1,2G
Gerig, 2M Styner,
3E
Kistner, 3Yueh-Yun Chi,
3K
Muller,
1JA
Lieberman
Depts. of 1Psychiatry, 2Computer Science, 3Biostatistics
University of North Carolina, Chapel Hill,
NC 27614, USA
[email protected] / http://www.cs.unc.edu/~gerig
SUMMARY
Object shape parameterization
Implied
Surface
Volume reduction of the hippocampus observed with MRI is one of the most
consistently described structural abnormalities in patients with
schizophrenia. However, the timing, the association with treatment, and an
intuitive explanation of morphologic changes are not known. This study
analyzed subtle changes of the hippocampal structure in schizophrenics
(N=57) as compared to matched controls (N=26). The effect of age, duration
of illness and drug type to local shape changes was studied with a new
shape representation technique and an exploratory statistical analysis.
Skeletal Mesh
(sampled)
Shape
representation by
sampled medial
mesh (M-rep). Mesh
represents shape
with over 99%
overlap.
Local Width
(Radius)
Features for Shape Analysis
Statistical analysis
M-rep 3x8 mesh
Tail
M-rep 3x8 mesh
Head
The M-rep shape representation model allows a separate analysis of shape
deformation and of local atrophy. The exploratory statistical model was a
repeated measures ANOVA, cast as a general linear multivariate model.
radius
The exploratory nature of the analysis means that the promising results must
be replicated in order to provide full confidence in the conclusions.
Radius: Local width
attribute (atrophy,
growth).
Deformation: Bending,
curvature change.
Subjects and Image Data
Statistical Model
Quantitative 1.5 Tesla MRI examinations of the brain were utilized to
examine a young patient group in the early illness stage of illness
(N=34) and an older group of schizophrenic patients who were
chronically ill (N=22). MRI examinations of the brain were also
acquired for 26 right-handed male controls matched to both patient
groups for age and handedness (young controls N=14, older controls
N=12). Patients were characterized with regards to duration of illness
and illness severity utilizing PANSS assessments. At the time of scan,
17 early illness patients were on typical antipsychotic medication
(haloperidol), and 17 were on atypical antipsychotic medications (13
olanzapine, 4 on risperidone). For chronic patients, only 5 were on
typical medications (3 haloperidol, 1 tri u-perazine and 1 thiothixene),
and 18 were on atypical medications (6 olanzapine, 8 clozapine and 4
risperidone).
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Statistical
analysis of
3x8 mesh
representati
on. Height
represents
difference.
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Comparison: Longitudinal Shape Change of Controls
RESULTS
Shape Deformation between Schizophrenics and Controls
Summary of Results
L/R Asymmetry of Radius Difference
This exploratory analysis on the 79 subject dataset demonstrates a new
technique for statistical analysis of shapes in combination with clinical
variables. Following this study, we will continue with an confirmatory analysis
in an independent schizophrenia study where all hypothesis would be
specified and fixed a priory before data would be collected. This study would
allow either replication or rejection of results shown here.
CONCLUSIONS
• New shape representation and statistical analysis scheme overcomes
problem of feature reduction/selection from high-dimensional shape
representation.
• Analysis does not require correction for multiple tests as in schemes using a
high number of surface-based statistical tests.
• Systematic integration of shape with age, duration of illness and drug effect
parameters  Leads to intuitive answers in regard to treatment effects and
longitudinal changes.
• Significant hippocampal deformation difference between schizophrenics and
controls (p<0.0091). Deformation increases with age. Differences are located
mostly in the tail and to a lesser extent in the head of the hippocampus.
• Drug treatment groups (Atypical, Typical) show significant differences of
Radius Asymmetry measure (Left-Right Radius difference). Decreasing
asymmetry of width with age is found.
• Deformation and width asymmetry changes in controls analyzed over a ten
years interval are not significant.
• Exploratory analysis
Given the expected atrophy over time due to aging, it seems that the
hippocampus of a young schizophrenic looks like the hippocampus of an
older control, and the two groups look more alike later in time. Furthermore,
the atypical treated patients start (at an early age) less far from the normals
than do those treated with typical drugs.
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References:
[1] A. Kelemen, G. Székely, and G. Gerig, „Three-dimensional Model-based Segmentation“, IEEE Transactions on Medical
Imaging (IEEE TMI), 18(10):828-839, Oct 1999
[2] G. Gerig, M. Styner, D. Jones, D. Weinberger, and J. Lieberman, “Shape Analysis of brain ventricles using SPHARM”,
in: Proc. Workshop on Mathematical Methods in Biomedical Image Analysis MMBIA 2001, IEEE Comp. Soc., pp. 171178, Dec. 2001
[3] G Gerig, M Styner, ME Shenton, JA Lieberman, Shape versus Size: Improved Understanding of the Morphology of
Brain Structures, Proc. MICCAI 2001, Springer LNCS 2208, pp. 24-32, Oct. 2001
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