Extraction of Landmarks and Features from Virtual Colon Models
Krishna Chaitanya Gurijala, Arie Kaufman, Wei Zeng Xianfeng Gu
Computer Science Department, Stony Brook University
Need for Feature Extraction?• Virtual Colonoscopy - CT scans are taken in
supine and prone positions • Colon has tube-like structure, flexible with lots
of twists and folds• Change of position results in drastic change in the
topology of the colon
Landmarks and features help in segmentation and understanding the surface of the colon and to confirm the polyp location.
Feature Extraction - Applications• Registration of supine-prone colon surfaces• Virtual colon navigation• Virtual colon dissection• Polyp matching• Segment wise comparison• Bookmarking the polyp location• Knowing the location of the user inside the
colon
Features
• Taeniae coli and flexures are anatomical landmarks that do not change despite the change in the position of the person
• We propose methods for the detection of these landmarks and internal feature points on the colon surface
• Landmarks and features help to toggle between corresponding positions in supine and prone
• Taeniae coli – three bands of longitudinal muscle on the surface of the colon
• Taeniae coli detection based on haustral fold detection
• Haustral folds detected using heat diffusion, curvature filter and connected components
Taeniae Coli Extraction
Taeniae Coli Extraction
• Using the haustral folds, taeniae coli are obtained by applying fuzzy C-means clustering algorithm iteratively
Detection of Flexures• Four flexures, two major and two minor :
A-T (Hepatic)T-D (Splenic)D-SS-R
Detection of Flexures• Projection of colon centerline onto a 2D
coordinate system in positive z-x and y-z planes• Bends in the centerline are identified by
iterative evaluation of slopes in the two planes• Only major bends are retained and sorted based on the z-coordinate
Detection of Flexures• Splenic flexure identified as the bend with
highest z-coordinate• Hepatic flexure identified as the bend with
second highest z-coordinate• Two other flexures between the descending
colon and sigmoid and between the sigmoid and rectum are identified similarly
Detection of Internal Features• The colon surface is opened up along the
taenia coli and cut along the flexures to obtain five flat anatomical segments
• For each of the flat segments, color encoded mean curvature images are generated
Segmentation• Folds – only tangible regions of interest• Use the graph cut algorithm to separate the
folds (blue color encoded) from the rest of the surface (red and green color encoded)
• Significant folds are retained by thresholding
Feature Points Detection
• Detected folds approximated as ellipses• The axial points of the folds are extracted as
the feature point set
Feature Matching• Feature matching formulated as energy
minimization problem – solved using dual decomposition technique
• Only the border feature points are considered for correspondence to overcome the possibility of any wrongly matched feature points
Conclusion• Anatomical landmarks namely taeniae coli and
flexures are located automatically and in robust manner – these are used for colon flattening and partitioning
• Feature points are automatically extracted from the flattened colon surface – correspondences are obtained between supine and prone
• These landmarks and feature points have various applications for the VC system
Thanks!
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