  We present a novel graph-theoretic method for small bowel path tracking. It
is formulated as finding the minimum cost path between given start and end
nodes on a graph that is constructed based on the bowel wall detection. We
observed that a trivial solution with many short-cuts is easily made even with
the wall detection, where the tracked path penetrates indistinct walls around
the contact between different parts of the small bowel. Thus, we propose to
include must-pass nodes in finding the path to better cover the entire course
of the small bowel. The proposed method does not entail training with
ground-truth paths while the previous methods do. We acquired ground-truth
paths that are all connected from start to end of the small bowel for 10
abdominal CT scans, which enables the evaluation of the path tracking for the
entire course of the small bowel. The proposed method showed clear improvements
in terms of several metrics compared to the baseline method. The maximum length
of the path that is tracked without an error per scan, by the proposed method,
is above 800mm on average.
