Short-term reproducibility of computed tomography-based lung density measurements in alpha-1 antitrypsin deficiency and smokers with emphysema.
OBJECTIVE
To study the short-term reproducibility of lung density measurements by multi-slice computed tomography (CT) using three different radiation doses and three reconstruction algorithms.


METHODS
Twenty-five patients with smoker's emphysema and 25 patients with alpha1-antitrypsin deficiency underwent 3 scans at 2-week intervals. Low-dose protocol was applied, and images were reconstructed with bone, detail, and soft algorithms. Total lung volume (TLV), 15th percentile density (PD-15), and relative area at -910 Hounsfield units (RA-910) were obtained from the images using Pulmo-CMS software. Reproducibility of PD-15 and RA-910 and the influence of radiation dose, reconstruction algorithm, and type of emphysema were then analysed.


RESULTS
The overall coefficient of variation of volume adjusted PD-15 for all combinations of radiation dose and reconstruction algorithm was 3.7%. The overall standard deviation of volume-adjusted RA-910 was 1.7% (corresponding to a coefficient of variation of 6.8%). Radiation dose, reconstruction algorithm, and type of emphysema had no significant influence on the reproducibility of PD-15 and RA-910. However, bone algorithm and very low radiation dose result in overestimation of the extent of emphysema.


CONCLUSIONS
Lung density measurement by CT is a sensitive marker for quantitating both subtypes of emphysema. A CT-protocol with radiation dose down to 16 mAs and soft or detail reconstruction algorithm is recommended.
Department of Respiratory Medicine, Gentofte Hospital, Hellerup, Denmark. saher@dadlnet.dk
S B
SB
Shaker
A
A
Dirksen
L C
LC
Laursen
N
N
Maltbaek
L
L
Christensen
U
U
Sander
N
N
Seersholm
L T
LT
Skovgaard
L
L
Nielsen
A
A
Kok-Jensen
D015502:Absorptiometry, Photon / Q000706:statistics & numerical data; D000368:Aged; D000465:Algorithms; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods / Q000706:statistics & numerical data; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology; D008176:Lung Volume Measurements / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011653:Pulmonary Diffusing Capacity / Q000502:physiology; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011829:Radiation Dosage; D012044:Regression Analysis; D015203:Reproducibility of Results; D012115:Residual Volume / Q000502:physiology; D012907:Smoking / Q000009:adverse effects*; D012984:Software; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000706:statistics & numerical data; D014109:Total Lung Capacity / Q000502:physiology; D019896:alpha 1-Antitrypsin Deficiency / Q000150:complications*