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LOGISMOS – Complex Topology and Multiple Object Interactions

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More than Rectangles and Tubes:Generalization to complex shapes Step 1: Pre-segmentation

Derive topology of objects of interest from image data approximate segmentation

Step 2: Mesh Generation Specify structure of a base graph defining neighboring relations among voxels

on the sought surfaces

Step 3: Image Resampling Resample along a ray intersecting every vertex of the mesh forming graph

columns.

Step 4: Graph Construction Weighted directed graph G built using from columns, with neighboring

relations, smoothness constraints, and inter-surface separation.

Step 5: Graph Search Searching for optimal closed set.

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Problems of Step 3 – Colliding Columns

Pre-segmented surface

True surface

Bifurcation Detection

An electric field theory motivated search direction

Non-intersecting

Easy to compute

Expanding to any positions

Non-ELF medial-surface approach also possible

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Electric Lines of Force (ELF)

rr

QEi ˆ

4

12

0

i iEE

Point charges

Iso-electric

fieldElectric lines of

force (ELF)

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3D Airway Double Surface

Inner surface Double surfaces

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Aortic Thrombus from MDCT

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Preliminary aortic/iliac lumen segmentation

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Cross-Object Interactions

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Multi-object 3D segmentation Regions of object-to-object interactions reflected in inter-graph arcs

Steps: Identify regions of pairwise interaction

Link interacting surfaces = create inter-graph arcs

Build/solve resulting graph

Example Prostate – Bladder – (Rectum)

Knee-joint cartilage segmentation Femur/Tibia/Patella cartilage thickness

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Prostate – Bladder SegmentationIn

put I

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Pre

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Sur

face

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raph

Fin

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Pre-segmentation

Graph Optimization

Healthy Knee

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Severe Osteoarthritis

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DEMO

Simultaneous segmentation of an object and up to two surfaces (MVCBCT)

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Mutually interacting terrain-like surfaces

and regions of arbitrary topology

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A lung tumor (orange) in megavoltage cone-beam CT

A lymph node (red) in X-ray CT data.