colon visualization using shape preserving flattening
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Colon Visualization Using Shape Preserving Flattening. Joseph Marino and Arie Kaufman Stony Brook University. Introduction. Virtual colonoscopy is a popular non-invasive colon screening method Various colon flattening methods proposed - PowerPoint PPT PresentationTRANSCRIPT
Colon Visualization UsingShape Preserving Flattening
Joseph Marino and Arie Kaufman
Stony Brook University
Introduction
• Virtual colonoscopy is a popular non-invasive colon screening method
• Various colon flattening methods proposed– Cylindrical projections of segments [Vilanova Bartoli et al.]
– Mass-spring unfolding [Umemoto et al.]
– Conformal mapping [Haker et al., Hong et al.]
• Need methods to visualize flattened colons
Related Work
• Visualize conformally flattened colon meshes– Shape characteristics are of utmost importance
• Polygonal rendering of flattened meshes– Use per-vertex normals of original surface mesh– Encode geometric properties as color at each vertex• E.g., curvature
• These methods do not have the quality or look of the VC endoluminal view
Generating 2D Views
• Use volumetric ray casting– Similar to endoluminal view
• Obtain view position for each ray– For each column of pixels in final image• Average original 3D positions of each pixel• These form a flattened centerline along the entire colon• Use these as view point for ray casting
(each column uses its average position value)
2D Surface Views
• Opaque transfer function– Typical colon surface view– Structures identifiable due to shape preserving map
• This rendering is more natural to view and of higher quality than a simple mesh rendering
Further 2D Views
• Using ray casting also allows for other rendering effects– E.g., electronic biopsy rendering
• Given two flattened colons with a one-to-one and onto correspondence, obtaining matching views in 2D is trivial
Integration for 3D Navigation
• Flattened colon can help guide 3D navigation
• For a location on the flattened colon, obtain the view frustum to view that location in the endoluminal view
• View position either on flattened centerline or volumetric skeleton
Obtaining View Frustums
𝑣0 = 𝑝− 𝑜ȁ�𝑝− 𝑜ȁ� , 𝑣1 = 𝑐1 − 𝑐0ȁ�𝑐1 − 𝑐0ȁ� , 𝑣2 = 𝑣0 × 𝑣1 ,
Given: location p on the surface viewpoint o on centerline (closest to p) neighboring centerline points c0 and c1
{o; v0, v1, v2}
Corresponding View FrustumsIf one-to-one and onto mapping between two flat colons
Given view frustum on supine, find corresponding view frustum in prone
Similar to previous 𝑣𝑝1 = 𝑝0 − 𝑜𝑝ห𝑝0 − 𝑜𝑝ห ,
𝑣𝑝0 = ൫𝑝1 − 𝑜𝑝൯× 𝑣𝑝1ห൫𝑝1 − 𝑜𝑝൯× 𝑣𝑝1ห , 𝑣𝑝2 = 𝑣𝑝0 × 𝑣𝑝1 ,
{op; vp0, vp1, vp2}
Conclusion
• Methods to integrate shape preserving flattening into VC system
• Flattened 2D view with same look and feel as typical 3D endoluminal view
• Use 2D flattened mesh to assist in navigation in the 3D endoluminal view
Acknowledgements
• This work has been supported by NIH grant R01EB7530 and NSF grants IIS0916235, CCF0702699.
• The datasets are provided through the NIH, courtesy of Dr. Richard Choi, Walter Reed Army Medical Center.
Questions & Answers