The Role of Computed Tomography for the Evaluation of Lung Disease in Alpha-1 Antitrypsin Deficiency

Figures

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  Figure 1. Visual depiction of the Hounsfield scale, representing the radiodensities of various tissues/materials.

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  Figure 2. CT densitometric measures of emphysema. A, Coronal slice of a normal lung and the distribution of Hounsfield units (HU). Note that the mean HU values for various lung zones (blue, green, and yellow lines) and whole lung (red) are approximately –850. B, Coronal slice of an emphysematous lung. Note that the HU values are now shifted toward –1,000 HU, the density of air.

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  Figure 3. Cumulative frequency distribution histogram of lung density at the 15th percentile (PD15) and voxel index (VI) defining emphysema as the percentage of low-attenuation areas below –950 HU (y axis).

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  Figure 4. CT sagittal slices from a smoker, showing progression of emphysema. A, Emphysema in both the left upper and lower lobes is seen (arrows) on baseline CT scan (mean whole-lung emphysema, 18.7%; lung density at 15th percentile, 40.2 g/L). B, Progression of the emphysematous destruction of the parenchyma is seen 5 years later (some areas are marked with arrowheads) (mean whole-lung emphysema, 32.3%; lung density at 15th percentile, 27.3 g/L). Case from the COPDGene Study.

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  Figure 5. Estimated lung density decline (adjusted lung density at 15th percentile at total lung capacity) over 48 months, using data from the mixed-effects regression model applied to each trial separately (the Randomized, Placebo-Controlled Trial of Augmentation Therapy in Alpha-1 Proteinase Inhibitor Deficiency [RAPID-RCT] and RAPID Open Label Extension [RAPID-OLE] trial intention-to-treat population).