  We present a new graph-based method for small bowel path tracking based on
cylindrical constraints. A distinctive characteristic of the small bowel
compared to other organs is the contact between parts of itself along its
course, which makes the path tracking difficult together with the indistinct
appearance of the wall. It causes the tracked path to easily cross over the
walls when relying on low-level features like the wall detection. To circumvent
this, a series of cylinders that are fitted along the course of the small bowel
are used to guide the tracking to more reliable directions. It is implemented
as soft constraints using a new cost function. The proposed method is evaluated
against ground-truth paths that are all connected from start to end of the
small bowel for 10 abdominal CT scans. The proposed method showed clear
improvements compared to the baseline method in tracking the path without
making an error. Improvements of 6.6% and 17.0%, in terms of the tracked
length, were observed for two different settings related to the small bowel
segmentation.
