@article {473201,
	title = {Trachea Air: Internal Reference Standard For CT Lung Densitometry},
	journal = {American journal of respiratory and critical care medicineAmerican journal of respiratory and critical care medicine},
	volume = {185},
	year = {2012},
	month = {Jun},
	pages = {A2037},
	abstract = {


RATIONALE: The nominal CT number of air is -1000HU. In contemporary multi-slice CT scanners, the CT number of air in the trachea is greater than -1000HU. Consequently, the value of trachea air CT number of an individual subject{\textquoteright}s image might be used as an internal reference standard for CT lung densitometry. 


},
	author = {Judy, Philip F and San Jose Est{\'e}par, Ra{\'u}l and Ross, James C and Washko, George R and Silverman, Edwin K and Lynch, David A and the COPDGene Investigators, \&}
}