Proceedings Article | 29 March 2007
KEYWORDS: Colon, Image registration, Image segmentation, Virtual colonoscopy, Bone, Diagnostics, Colorectal cancer, Computer aided diagnosis and therapy, Detection and tracking algorithms, Computer aided design
CT colonography, a prevalent tool to diagnose colon cancer in its early stages,
is often limited by bad distention, or retained fluids, which
will cause segments of the colon to be impossible to process by CAD tools.
By scanning patients in both prone and supine positions, collapsed segments
and retained fluids will not be in the same place in both images, increasing
the length of the colon that can be processed correctly. In order to fully use
these two scans, they must be registered, so that a lesion identified on one of
them can be mapped to the other, thus increasing sensitivity and specificity of
CAD tools.
The surface of the colon is however large (more than half a million vertices
on our images), and has no canonical shape, which makes atlases and other
widely used registration algorithms non optimal. We present in this paper a
fast method to register the colon surface between prone and supine scans using
landmarks present on the colon, the teniae coli. Our method is composed
of three steps. First, we register the body, based on manually placed
landmarks. Then we register the three teni&tildeae; coli, and, from this
registration, we compute a deformation field for each vertex of the colon
surface.
We tested our method on 5 cases, by measuring the RMS error after body
registration, quantifying the intrisic movement of the colon, and after colon
surface registration. The RMS error was reduced from 1.8 cm to 0.49 cm, a
reduction of 71%.
