Efficient colon wall flattening by improved conformal mapping methodologies for computed tomography colonography

Conformal mapping provides a unique way to flatten the three-dimensional (3D) colon wall. Visualizing the flattened colon wall supplies an alternative means for the task of detecting abnormality as compared to the conventional endoscopic views. In addition to the visualization, the flattened colon wall carries supplementary geometry and texture information for computer aided detection of abnormality. It is hypothesized that utilizing both the original and the flattened 3D colon walls shall improve the detection capacity of currently available computed tomography colonography. Two major challenges exist for the conformal mapping: (1) accuracy in preserving the essential geometry and (2) efficiency in computing the mapping. This paper describes an improved conformal mapping algorithm over our previous work to accelerate the computing speed and increase the calculation accuracy. Starting from a segmented colon wall, a centerline-based search strategy is applied to remove outliers or topological noise on the segmented colon wall. The de-noised wall is then flattened by the improved conformal mapping algorithm. The algorithm was tested by patient datasets with comparison to our previous algorithm. By a PC platform of 3.0GHz CPU and 8.0 GB ROM memory, the speed was accelerated from more than 70 minutes to less than 5 minutes. In addition to the gain in speed, improvement in accuracy is observed. The gained speed and accuracy are crucially important because of the current challenges in detecting small polyps in the desired high sensitivity and efficiency for screening purpose.