PURPOSE: To compare the computed tomographic (CT) lung densitometry re
sults in patients with chronic obstructive pulmonary disease (COPD) an
d in control subjects (healthy persons). MATERIALS AND METHODS: Spirom
etrically gated CT sections at 5 cm above and 5 cm below the carina at
90% and 10% vital capacity (VC) were imaged in patients and controls.
Various densitometric parameters were derived from the CT data, and r
esults were compared between the two levels of inspiration. RESULTS: D
ensitometric results in patients with emphysema were substantially dif
ferent from those in patients with chronic bronchitis and in controls
at 90% and 10% VC. Differences in patients with chronic bronchitis and
in controls were not significant at 90% VC but were significant at 10
% VC (P < .001). The mean changes in densitometric parameters between
90% and 10% VC were substantially greater in controls than in patients
with COPD. CONCLUSION: It may be possible to classify lung disease wi
th only two CT sections obtained at the same anatomic level one at 90%
and one at 10% VC, irrespective of the densitometric parameter used.