Quantitative Emphysema Distribution in Anatomic and Non-anatomic Lung Regions.

Owsijewitsch, Michael; Ley-Zaporozhan, Julia; Kuhnigk, Jan-Martin; Kopp-Schneider, Annette; Eberhardt, Ralf; Eichinger, Monika; Heussel, Claus Peter; Kauczor, Hans-Ulrich; Ley, Sebastian

PURPOSE The change of emphysema distribution with increasing COPD severity is not yet assessed. Especially, involvement of the upper aspect of the lower lobe is unknown. The primary aim was to quantitatively determine regional distribution of emphysema in anatomically (lung lobes) and non-anatomically defined lung regions (upper/lower lung halves as well as core and rind regions) in a cohort covering equally all COPD severity stages using CT. MATERIAL AND METHODS Basically 100 CT data sets were quantitatively evaluated for regional distribution of emphysema. Emphysema characteristics (emphysema index, mean lung density and 15th percentile of the attenuation values of lung voxels) were compared (t-test) in: upper lobes vs. upper halves, lower lobes vs. lower halves, core vs. rind region. RESULTS In patients with ≤ GOLD II, a significantly higher emphysema burden was found in the upper lobes as compared to upper halves. In subjects with GOLD III/IV the differences were not significant for all emphysema characteristics. A high difference between lobes and halves in subjects with ≤ GOLD II was found, in contrast to low difference in higher GOLD stages. CONCLUSIONS Lobar segmentation provides improved characterization of cranio-caudal emphysema distribution compared to a non-anatomic approach in subjects up to GOLD stage II.