To determine whether ultralow dose chest CT with tin filtration can
be used for emphysema quantification and lung volumetry and to
assess differences in emphysema measurements and lung volume between
standard dose and ultralow dose CT scans using advanced modeled
iterative reconstruction (ADMIRE).
84 consecutive patients from a prospective, IRB-approved
single-center study were included and underwent clinically indicated
standard dose chest CT (1.7±0.6mSv) and additional
single-energy ultralow dose CT (0.14±0.01mSv) at 100kV and
fixed tube current at 70mAs with tin filtration in the same session.
Forty of the 84 patients (48%) had no emphysema, 44 (52%) had
emphysema. One radiologist performed fully automated software-based
pulmonary emphysema quantification and lung volumetry of standard
and ultralow dose CT with different levels of ADMIRE. Friedman test
and Wilcoxon rank sum test were used for multiple comparison of
emphysema and lung volume. Lung volumes were compared using the
concordance correlation coefficient.
The median low-attenuation areas (LAA) using filtered back
projection (FBP) in standard dose was 4.4% and decreased to 2.6%,
2.1% and 1.8% using ADMIRE 3, 4, and 5, respectively. The median
values of LAA in ultralow dose CT were 5.7%, 4.1% and 2.4% for
ADMIRE 3, 4, and 5, respectively. There was no statistically
significant difference between LAA in standard dose CT using FBP and
ultralow dose using ADMIRE 4 (p=0.358) as well as in standard dose
CT using ADMIRE 3 and ultralow dose using ADMIRE 5 (p=0.966). In
comparison with standard dose FBP the concordance correlation
coefficients of lung volumetry were 1.000, 0.999, and 0.999 for
ADMIRE 3, 4, and 5 in standard dose, and 0.972 for ADMIRE 3, 4 and 5
in ultralow dose CT.
Ultralow dose CT at chest X-ray equivalent dose levels allows for
lung volumetry as well as detection and quantification of emphysema.
However, longitudinal emphysema analyses should be performed with
the same scan protocol and reconstruction algorithms for
Messerli M, Ottilinger T, Warschkow R, Leschka S, Alkadhi H,
Wildermuth S, Bauer R. Emphysema quantification and lung volumetry
in chest X-ray equivalent ultralow dose CT - Intra-individual
comparison with standard dose CT. Eur J Radiol 2017; 91:1-9.