NA-MICNational Alliance for Medical Image Computing

Preliminary Analysis ofHippocampal Shape fromNAMIC Darmouth Data

Processing: Martin Styner

Data: Andy Saykin

National Alliance for Medical Image Computing http://na-mic.org

General Items

• UNC shape pipeline worked without any modification on the Dartmouth data

• Processing pipeline not yet ready for Core 3 since no point&click User Interface

• Hippocampal shape highly variable in data– I expect the need for a larger dataset in order

to show consistent, reliable shape differences

• Timeline– Data received: Sept 8 2005– This report with full results: Sept 14 2005

National Alliance for Medical Image Computing http://na-mic.org

Shape Analysis Workflow

Hippocampus Segmentation

Preprocessing &Parameterization

SPHARM-PDM Shape

QCShape &Corresp.

Alignment& Scale

Feature Computatione.g. Subdivision or

Mean Shape Difference

QC of Features & Statistical Results

Statistical AnalysisOf Features

National Alliance for Medical Image Computing http://na-mic.org

Pre-processing

• Sample case• Segmentation

after pre-processing (establishing spherical topology)

• 0.5mm^3 resolution

National Alliance for Medical Image Computing http://na-mic.org

SPHARM Shape

• Spherical parametrization• Mirroring of right hippocampus• Alignment to first order ellipsoid• Alignment to template

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

National Alliance for Medical Image Computing http://na-mic.org

SPHARM Shape

• Overlay of voxel segmentation (red) with SPHARM (blue)

• Average Error ~ 0.12mm

National Alliance for Medical Image Computing http://na-mic.org

SPHARM Correspondence

National Alliance for Medical Image Computing http://na-mic.org

SPHARM Mean Hippo

Overall Mean Left Mean Right Mean

National Alliance for Medical Image Computing http://na-mic.org

Asymmetry: MeshValmet

Left vs RightAsymmetry ofMean Shapes(only 6 cases)

National Alliance for Medical Image Computing http://na-mic.org

Statistical Testing

• Only 6 cases: Do not interprete this data, it’s just an example

• Global p-value for asymmetry shape difference: 0.34

Mean difference Raw p-valueMean Overlay

National Alliance for Medical Image Computing http://na-mic.org

Hippocampal Subdivision

• Skeleton based Subdivision (11 parts)

• Fusion into 3 (head, body, tail) or 5 parts (ant/post head, ant/post body, tail)

National Alliance for Medical Image Computing http://na-mic.org

Hippocampal Subdivision

• Subdivision Automatic QC images

National Alliance for Medical Image Computing http://na-mic.org

Hippocampal SubdivisionNAMIC01 l hippo 0 4477 423 1850 2204

NAMIC02 l hippo 0 3895 311 1642 1942

NAMIC03 l hippo 0 4398 336 2054 2009

NAMIC04 l hippo 0 3621 329 1566 1726

NAMIC05 l hippo 0 2610 265 1147 1198

NAMIC06 l hippo 0 3263 301 1412 1549

NAMIC01 r hippo 1 4788 368 2099 2322

NAMIC02 r hippo 1 4747 361 2103 2283

NAMIC03 r hippo 1 4168 315 1903 1949

NAMIC04 r hippo 1 3416 291 1465 1660

NAMIC05 r hippo 1 3315 294 1466 1556

NAMIC06 r hippo 1 3787 316 1640 1831

Total Tail Body Head

Mean Right 4037 324 1779 1934

Mean Left 3711 327 1612 1771

P-value Asymmetry 0.14 0.84 0.15 0.10

National Alliance for Medical Image Computing http://na-mic.org

Hippocampal subdivision

• Agreement with local shape analysis

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Trend

P < 0.5

National Alliance for Medical Image Computing http://na-mic.org

Conclusion SPHARM

• Success! (ALL images in this ppt are from Darmouth hippocampus data)

• Hippocampus shape is variable, but correspondence and alignment worked very nicely

• Of course, no real analysis was possible with 6 datasets, but asymmetry analysis shows good example