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Segmentation and Parametric Modeling of the Human Spine Brian Dragone and Brian Wojciechowski Department of Industrial & Manufacturing Engineering, Western Michigan University, Kalamazoo, MI 49008

Problem Statement:

Results and Discussion:

Three dimensional representations are needed for analysis of the human spine in order to gain a greater understanding of its biomechanics.

• Given CT scans were incorrectly scaled • Spinal anomaly of transitional Lumbosacral vertebra • Endplates were severely ossified

Objectives:

Conclusions:

• Develop 3D models of spine • Parameterize models for hypothetical situations • Document process for repeatability

Anatomical Geometry: • Endplates: Top and bottom portions of the vertebral bodies that interface with the vertebral discs. The vertebral end plate is composed of a layer of thickened cancellous bone. • Vertebra Centroid: The point half way between the centers of the two endplates of a vertebra • Vertebral Body Line: The 3-D curved line that passes through the centroids of the vertebral bodies. • Analytic Ferguson Method: For a projection of the vertebral body line in a specific plane; angle between lines drawn from inflectional points to the apical point.

• • • • (Left) Label map of segmented CT scans (Center) Sagittal view and (Right) Coronal Views of final models

Data Segmentation: •Import CT scan data to 3DSlicer for initial display •Determine threshold parameter to extract each element •Eliminate extraneous data from segmented models

Endplate Placement: • Imported final 3D Slicer STL models into ATOS • Selected endplate surface points • Derived planes using linear regression models within ATOS

Parametric Assembly: Methodology:

•Used Pro/Program to specify parameters for clinical condition •Patterned Vertebra Centroid’s location, and define parametric graph as Vertebral Body Line •Programmed parametric assembly by specifying translation and rotation of vertebral bodies •Derived Ferguson Angle for defined scoliosis condition

• Segmented imagery acquired from Computed Tomography (CT) scans using 3D Slicer • Imported stereolithography (.STL ) files into ATOS software for placement and orientation of geometric features • Parameterized features in Pro/Engineer to simulate hypothetical curvatures and angular severities

IME 4920 – Spring 2010

3D models are fully completed The designed process allows for variable geometry Reduces time and effort required to manipulate model Current models are available for immediate analysis

(Left) Initial and programmed models (Top Right) Sample of programmed relations within Pro/Engineer (Bottom Right) Curvature graph and parameterized dimensions.

Recommendations: • Obtain desirable image volumes and repeat process to obtain variable model • Develop Finite Element meshes for analysis from delivered models • Simulate soft tissues and accommodate for changing distances between vertebra

Acknowledgements:

Endplate planar creation process using ATOS best-fit capabilities

We would like to thank the following people: • Dr. Jorge Rodriguez, IME Advisor • Dr. Peter Gustafson, MAE Advisor • Dr. Betsy Aller, IME Course Advisor • Dr. Mitchel Keil, IME Faculty • Dr. Richard Hathaway, MAE Faculty


Segmentation and Parametric Modeling of the Human Spine