Source:http://linkedlifedata.com/resource/umls/id/C1552913
NCI: A unit of cross-sectional measurement of a round area equal to the area of a circle with a diameter of one mil, approximately 0.785 398 square mils, or 506.707 square micrometers.,HL7V3.0: <p>1 [pi]/4.[mil_i]2</p>