Computer aided detection for low-dose CT colonography

Abstract

The paper describes a method for automatic detection of colonie polyps, robust enough to be directly applied to low-dose CT colonographic datasets. Polyps are modeled using gray level intensity profiles and extended Gaussian images. Spherical harmonic decompositions ensure an easy comparison between a polyp candidate and a set of polypoid models, found in a previously built database. The detection sensitivity and specificity values are evaluated at different dose levels. Starting from the original raw-data (acquired at 55mAs), 5 patient datasets (prone and supine scans) are reconstructed at different dose levels (down to 5mAs), using different kernel filters and slice increments. Although the image quality decreases when lowering the acquisition mAs, all polyps above 6mm are successfully detected oven at 15mAs. Accordingly the effective dose can be reduced from 4.93mSv to 1.61mSv, without affecting detection capabilities, particularly important when thinking of population screening. © Springer-Verlag Berlin Heidelberg 2005.