• whole-lung densitometry
• pulmonary emphysema
• lung cancer screening
• computed tomography

Objectives.
To evaluate pulmonary smoking-related parenchymal changes with two different software application in asymptomatic subjects enrolled in the ITALUNG randomized screening trial for early diagnosis of lung cancer using low-dose computed tomography (LDCT).
The aim of the study was to determine if a novel texture and local volumetric histogram feature-based analysis software (CALIPER) that can also quantify fibrosis and other visual features is comparable with a commercially available software designed to exclusively evaluate low attenuation based on threshold values and global histogram analysis (InSpace, Siemens). Specifically, the potential to demonstrate parenchymal features and changes in relation with smoking habits over time was evaluated.
Methods and Materials.
284 subjects randomized into the active arm of the ITALUNG trial underwent 2 lung LDCT examinations 2 years apart; at enrolment (T1, baseline) and the third (T3) round.
LDCT parameters analysed with two different software were: total lung volume (ml); % of Relative Areas (RA) -950 HU and 15th percentile (HU).
Subjects were divided in four subgroups on the basis of smoking habits: persistent smokers, former smokers, restarters and quitters.
Results:
In the whole population CALIPER demonstrated an increase of the RA -950 from T1 to T3 (%RA-950 = 21.3 at T1 and 22.4 at T3, p<.0001) and a decrease of 15th percentile HU (-966.6 at T1 and -969.4 at T3, p<.0001). In the four smoking-habits subgroups CALIPER showed a significant progression of %RA-950 in particular an increase of RA -950 in persistent smokers (19.4 T1 to 20.1 T3, p=0.004), in former smokers (24.9 T1 to 25.9 T3, p=0.005) and in quitters (20.0 T1 to 23.8 T3, p<.0001). In 7 restarters was observed a non-significant decrease of %RA-950 (19.3 T1 to 16.0 T3, p=0.13).
The commercial software longitudinally demonstrated a similar increase of the %RA -950 from T1 to T3 (%RA-950 = 21.4 at T1 and 22.6 at T3, p<.0001) and decrease of the 15th percentile HU (-966,6 at T1 and -970.1 at T3, p<.0001) and same trends in the four subgroups.
Conclusion:
During this short-term follow up CALIPER quantified parenchymal density changes nearly equivalent to the commercial software in asymptomatic subjects and in the four subgroup of smokers. However, in addiction, CALIPER allowed the characterization of severity of low attenuation areas (mild, moderate or severe) and quantification of other lung abnormalities such as honeycombing, reticulation and ground-glass opacity that are not available in the other software analysis.