Assessment of regional progression of pulmonary emphysema with CT densitometry.
BACKGROUND
Lung densitometry is an effective method to assess overall progression of emphysema, but generally the location of the progression is not estimated. We hypothesized that progression of emphysema is the result of extension from affected areas toward less affected areas in the lung. To test this hypothesis, a method was developed to assess emphysema severity at different levels in the lungs in order to estimate regional changes.


METHODS
Fifty subjects with emphysema due to alpha(1)-antitrypsin deficiency (AATD) [AATD deficiency of phenotype PiZZ (PiZ) group] and 16 subjects with general emphysema (general emphysema without phenotype PiZZ [non-PiZ] group) were scanned with CT at baseline and after 30 months. Densitometry was performed in 12 axial partitions of equal volumes. To indicate predominant location, craniocaudal locality was defined as the slope in the plot of densities against partitions. Regional progression of emphysema was calculated after volume correction, and its slope identifies the area of predominant progression. The hypothesis was tested by investigating the correlation between predominant location and predominant progression.


RESULTS
As expected, the PiZ patients showed more basal emphysema than the non-PiZ group (craniocaudal locality, - 40.0 g/L vs - 6.2 g/L). Overall progression rate in PiZ patients was lower than in non-PiZ subjects. A significant correlation was found between craniocaudal locality and progression slope in PiZ subjects (R = 0.566, p < 0.001). In the non-PiZ group, no correlation was found.


CONCLUSIONS
In the PiZ group, the more emphysema is distributed basally, the more progression was found in the basal area. This finding suggests that emphysema due to AATD spreads out from affected areas.
Bakker
M Els
ME
Division of Image Processing, Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands. Electronic address: m.e.Bakker@lumc.nl.
Putter
Hein
H
Department of Medical Statistics, Leiden University Medical Center, Leiden, the Netherlands.
Stolk
Jan
J
Department of Pulmonology, Leiden University Medical Center, Leiden, the Netherlands.
Shaker
Saher B
SB
Department of Respiratory Medicine, Gentofte University Hospital, Hellerup, Denmark.
Piitulainen
Eeva
E
Department of Pulmonary Medicine and Allergology, Malmö University Hospital, Malmö, Sweden.
Russi
Erich W
EW
Pulmonology Division, University Hospital Zurich, Zurich, Switzerland.
Stoel
Berend C
BC
Division of Image Processing, Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands.
D003720:Densitometry / Q000379:methods*; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011656:Pulmonary Emphysema / Q000097:blood / Q000000981:diagnostic imaging* / Q000209:etiology; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*; D000515:alpha 1-Antitrypsin / Q000097:blood; D019896:alpha 1-Antitrypsin Deficiency / Q000097:blood / Q000150:complications
D000515:alpha 1-Antitrypsin