An Interactive Virtual Endoscopy ToolWith Automated Path Generation

Delphine Nain, MIT AI Laboratory.

Thesis Advisor: W. Eric. L Grimson, MIT AI Laboratory.

Presentation Overview

• Background and Motivation

• Interactive System• Central Path Planning Algorithm• Synchronized Virtual Endoscopy

• Conclusion

Medical Motivation

• Cancer is the 2nd cause of death in the US• 43 % of people have a risk to be diagnosed with

cancer– Out of those 88 % are cancer in inner organ

• How can “see” inside the body to

screen and cure?

Conventional Endoscopy

• advantages:– minimally invasive– high resolution– interactivity

•disadvantages:

–can be painful and uncomfortable

–limited exploration

Conventional Medical Imaging

Conventional Visualization

• advantages: – non invasive– information on tissue shape

through and beyond walls of organ

•disadvantages:

–mentally align contiguous slides

–lower resolution than video

Segmentation: Volume

3D Reconstruction : Model

3D Visualization

Virtual Endoscopy

• Combines strengths of previous alternatives on patient-specific dataset– Spatial exploration– Cross-correlation with original

volume

Compact and Intuitive way to explore huge amount of information

Virtual Endoscopy: advantages

• clinical studies:– planning and post-operation: generates views that are not

observable in actual endoscopic examinations– color coding algorithms give supplemental information

Virtual Colonoscopy

System Requirements

• Combination of Interactivity and Automation is key

• Cross Reference between 3D models and grayscale volumes

Presentation Overview

• Background and Motivation

• Interactive System• Central Path Planning Algorithm• Synchronized Virtual Endoscopy

• Conclusion

Display

Navigation Interface

Cross Reference

Provided by Arjan Welmers

Path: Update

Applications: Middle Ear

Thomas RodtSoenke Bartling

Applications: Cardiovascular

Provided by Bonglin Chung

Presentation Overview

• Background and Motivation

• Interactive System• Central Path Planning Algorithm• Synchronized Virtual Endoscopy

• Conclusion

Automated Path Planning

• Goal:

provide a “create path” button that

produces a centerline inside a 3D

model of any topology

Input

Output

Step 1: Produce a Labelmap

Step 2: Produce a distance map

Step 3: Create a Graph

Create a Graph description of the Distance Map

• Nodes are voxels inside the model• Edge weight are 1/(distance)2 from the

wall of the organ

Step 4: Run modified Dijkstra

Dijkstra algorithm is a single source

shortest path algorithm

• We use a binary heap• An optimization: keep an evolving front,

stop when reach the end node

Step 5: Results

Running Time: ~7s

Step 5: Results

Running Time: ~3s

Presentation Overview

• Background and Motivation

• Interactive System• Central Path Planning Algorithm• Synchronized Virtual Endoscopy

• Conclusion

Synchronized Virtual Colonoscopy

Dynamic Programming

Results

Conclusion

• Combination of Automation and Interactivity is key

• Cross Reference is important• Synchronized Fly-Throughs is

novel contribution

Publication: D. Nain, S. Haker, E. Grimson, R. Kikinis

“An Interactive Virtual Endoscopy Tool”,

IMIVA workshop, MICCAI 2001.

Acknowledgements• Ron Kikinis• Steve Haker• Lauren O’Donnell• David Gering• Carl-Fredrik Westin• Peter Everett• Sandy Wells• Eric Cosman• Polina Golland• Soenke Bartling• John Fisher• Mike Halle• Ferenc Jolesz

Thank You!

Steve Haker, Hoon Ji, Connie Sehnert

Correspondance

0 0 0 1

x x x x

y y y y

z z z z

VPN VP VU p

VPN VP VU p

VPN VP VU p

T is transformation matrix (translation or rotation along local axis)

VC =

To uniquely determine the coordinates of the virtual camera:

• coordinates of camera: VCnew = VCold * T

• coordinates of the focal point:

FPnew = VCnew * T

Cross Reference

Provided by Arjan Welmers

3D Visualization

Synchronized Virtual Endoscopy