I am reading the paper
"A Method for Extraction of Bronchus Regions from 3D Chest X-ray CT Images by Analyzing Structural Features of the Bronchus" by Takayuki KITASAKA, Kensaku MORI, Jun-ichi HASEGAWA and Jun-ichiro TORIWAKI
and I run into a term I do not understand:
In equation (2), when we say "[] expresses the Gauss sign", what does it mean?