The effects of age, sex, lung size, and hyperinflation on CT lung densitometry.
OBJECTIVE
To test our proposal that, on high-resolution CT scans, the relative area of the lung with attenuation values lower than -950 H (RA950) can be a measurement of pulmonary emphysema, we examine the possible influences of sex, age, lung size, and hyperinflation on CT lung densitometry.


METHODS
The RA950 and the mean lung density (MLD) were measured in 42 healthy subjects (21 men, 21 women) from 23 to 71 years old, in 10 patients with asthma before and after a bronchial challenge test, and in seven patients with asthma who have irreversible hyperinflation (defined as an increased total lung capacity).


RESULTS
In the healthy subjects, we found no significant difference between sexes and no significant correlation between age and the MLD, but we found a significant correlation between age and the RA950. In addition, we found a significant correlation between the total lung capacity expressed as absolute values and both the RA950 and the MLD. We did not observe any effect of acute airflow limitation either on the MLD or on the RA950 in the asthmatic subjects after the bronchial challenge test. Likewise, we observed no change in either the MLD or the RA950 in the asthmatic subjects with chronic hyperinflation.


CONCLUSIONS
This study shows that CT lung densitometry is influenced by total lung capacity and, to a lesser degree, by age. Thus, this study suggests that normal CT attenuation values for the lung should be established.
Department of Radiology, Erasme University Hospital, Brussels, Belgium.
P A
PA
Gevenois
P
P
Scillia
V
V
de Maertelaer
A
A
Michils
P
P
De Vuyst
J C
JC
Yernault
D015502:Absorptiometry, Photon; D000328:Adult; D000367:Age Factors; D000368:Aged; D001249:Asthma / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D001985:Bronchial Provocation Tests; D002908:Chronic Disease; D005260:Female; D005652:Functional Residual Capacity; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011653:Pulmonary Diffusing Capacity; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D012123:Pulmonary Ventilation; D011856:Radiographic Image Enhancement; D012119:Respiration; D012737:Sex Factors; D014057:Tomography, X-Ray Computed; D014109:Total Lung Capacity; D014797:Vital Capacity