Assertion: polyp | /r/HasProperty | visualized through the head
Facets:
Source sentences:
text: The Mexican hat sign is formed by the appearance of 2 concentric rings; the outer ring represents the "en face" visualization of barium coating the surface of the head of a pedunculated polyp , while the inner ring represents a meniscus of barium surrounding the stalk of the polyp visualized through the head (Figure 21).