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AJR Am J Roentgenol. 2007 Jan;188(1):42-7.

Comparison of standard- and low-radiation-dose CT for quantification of emphysema.

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  • 1Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 S Kingshighway Blvd., St. Louis, MO 63110, USA. gieradad@wustl.edu



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


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.


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.


Low-dose technique has minimal effect on CT quantification of emphysema.

[PubMed - indexed for MEDLINE]
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