Comparison of standard- and low-radiation-dose CT for quantification of emphysema.
OBJECTIVE
This study was performed to compare standard- and low-radiation-dose techniques in the CT quantification of emphysema.


METHODS
The study population consisted of 36 men and 20 women who were current or former heavy smokers and underwent standard-dose (effective tube current, 100-250 mAs) chest CT at our institution within 6 months of having undergone low-dose (effective tube current, 30-60 mAs) chest CT. All CT scans were reconstructed at 5-mm slice thickness with a smooth filter. CT-measured lung volume, mean and median lung attenuation, and percentage of lung volume with attenuation lower than multiple thresholds (emphysema index values) were compared by Pearson correlation, two-tailed and paired Student's t tests, and regression analysis.


RESULTS
There were no significant differences in mean attenuation (-848 vs -846 H, p > 0.35) for the low dose and the standard dose or in median lung attenuation (-879 vs -878 H, p > 0.66). Low- and standard-dose emphysema indexes were correlated at all attenuation thresholds (r = 0.86-0.97). Mean emphysema indexes were higher on the low-dose scans, but the mean difference at all thresholds was less than 3%. The differences were significant (p < 0.05) only at the lower index thresholds, correlated with differences in lung volume (r < or = 0.86), and increased with greater differences in dose.


CONCLUSIONS
Low-dose technique has minimal effect on CT quantification of emphysema.
Gierada
David S
DS
Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S Kingshighway Blvd., St. Louis, MO 63110, USA. gieradad@wustl.edu
Pilgram
Thomas K
TK
Whiting
Bruce R
BR
Hong
Cheng
C
Bierhals
Andrew J
AJ
Kim
Jin Hwan
JH
Bae
Kyongtae T
KT
D000368:Aged; D004307:Dose-Response Relationship, Radiation; D004646:Emphysema / Q000000981:diagnostic imaging*; D006801:Humans; D008875:Middle Aged; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods*; D011874:Radiometry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*