CEA test: Carcinoembryonic antigen test is to detect response to therapy in cancer patients, especially colon cancer, with normal range of less than 2.5 (less than 5 in heavy smokers). Note that a positive test may not always be indicative of cancer.
Os Trigonum Syndrome. An Os Trigonum is a small, extra bone found at the back of the ankle in approximately 5-10% of people. Often it goes completely unnoticed, not causing any problems.
The apothem of a polygon is a line from the center to the midpoint of a side. This is also the inradius-the radius of the incircle (see below). See Apothem of a Polygon. Radius (circumradius). The radius of a regular polygon is a line from the center to any vertex. It is also the radius of the circumcircle of the polygon (see below). See Radius of a Polygon. Incircle. The incircle is the largest circle that will fit inside a regular polygon.