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. 2023 Mar 11;164(2):339–354. doi: 10.1016/j.chest.2023.02.049

Figure 14.

Figure 14

A, B, Parametric response mapping: deformable image registration (A) is used to match voxels on inspiratory and expiratory scans, and voxels are assigned a parametric response mapping category based on their HU values on the expiratory and corresponding registered inspiratory scan (B). For example, a voxel with a value of > –950 HU on the registered inspiratory scan and < –856 HU on the expiratory scans would be classified as fSAD. fSAD = functional small airways disease; HU = Hounsfield unit.