Low Attenuation Area (LAA%) LAA is a measure of lung density, defined as the % of voxels below a given threshold (usually -950, -920, or -910 HU). LAA serves as a surrogate measurement of emphysema and is able to localize these areas to specific regions of the lung, thirds, lobes, or sub-lobes. LAA provides more precision as to the extent and distribution of emphysema and is more objective and repeatable than a visual radiology read.
