Cystic Fibrosis: Are Volumetric Ultra-Low-Dose Expiratory CT Scans Sufficient for Monitoring Related Lung Disease?

CT scores from inspiratory and expiratory scans match closely, suggesting that end-expiratory CT alone may suffice for assessing cystic fibrosis–related structural abnormalities, thus helping to reduce radiation dose by up to 75%.


To assess whether chest computed tomography (CT) scores from ultra-low-dose end-expiratory scans alone could suffice for assessment of all cystic fibrosis (CF)-related structural lung abnormalities.

Materials and Methods

In this institutional review board–approved study, 20 patients with CF aged 6–20 years (eight males, 12 females) underwent low-dose end-inspiratory CT and ultra-low-dose end-expiratory CT. Informed consent was obtained. Scans were randomized and scored by using the Brody-II CT scoring system to assess bronchiectasis, airway wall thickening, mucus plugging, and opacities. Scoring was performed by two observers who were blinded to patient identity and clinical information. Mean scores were used for all analyses. Statistical analysis included assessment of intra- and interobserver variability, calculation of intraclass correlation coefficients (ICCs), and Bland-Altman plots.


Median age was 12.6 years (range, 6.3–20.3 years), median forced expiratory volume in 1 second was 100% (range, 46%–127%) of the predicted value, and median forced vital capacity was 99% (range, 61%–123%) of the predicted value. Very good agreement was observed between end-inspiratory and end-expiratory CT scores for Brody-II total score (ICC = 0.96), bronchiectasis (ICC = 0.98), airway wall thickening (ICC = 0.94), mucus plugging (ICC = 0.96), and opacities (ICC = 0.90). Intra- and interobserver agreement were good to very good (ICC range, 0.70–0.98). Bland-Altman plots showed that differences in scores were independent of score magnitude.


In this pilot study, CT scores from end-expiratory and end-inspiratory CT match closely, suggesting that ultra-low-dose end-expiratory CT alone may be sufficient for monitoring CF-related lung disease. This would help reduce radiation dose for a single investigation by up to 75%.

© RSNA, 2009


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Article History

Received February 25, 2009; revision requested April 9; revision received May 4; accepted May 8; final version accepted May 26.
Published in print: Oct 2009