Lung hyperinflation quantitated by chest CT in children with bronchiolitis obliterans syndrome following allogeneic hematopoietic cell transplantation.

OBJECTIVES: Bronchiolitis obliterans syndrome (BOS) diagnosis in children following allogeneic hematopoietic stem cell transplantation (post-HSCT) is based on detection of airway obstruction on spirometry and air-trapping, small airway thickening or bronchiectasis on chest CT. We assessed the relationship between spirometry indices and low-attenuation lung volume at total lung capacity (TLC) on CT. METHODS: Data of children post-HSCT with and without BOS were analyzed. An age-specific, low-attenuation threshold (LAT) was defined as average of (mean-1SD) lung parenchyma attenuation of 5 control subjects without lung disease matched to each age subgroup of post-HSCT patients. % CT lung volume at TLC with attenuation values

Low- and High-Attenuation Lung Volume in Quantitative Chest CT in Children without Lung Disease.

In contrast to studies of adults with emphysema, application of fixed thresholds to determine low- and high-attenuation areas (air-trapping and parenchymal lung disease) in pediatric quantitative chest CT is problematic. We aimed to assess age effects on: (i) mean lung attenuation (full inspiration); and (ii) low and high attenuation thresholds (LAT and HAT) defined as mean attenuation and 1 SD below and above mean, respectively. Chest CTs from children aged 6-17 years without abnormalities were retrieved, and histograms of attenuation coefficients were analyzed. Eighty examinations were included. Inverse functions described relationships between age and mean lung attenuation, LAT or HAT (p < 0.0001). Predicted value for LAT decreased from -846 HU in 6-year-old to -950 HU in 13- to 17-year-old subjects (cut-off value for assessing emphysema in adults). %TLCCT with low attenuation correlated with age (rs = -0.31; p = 0.005) and was <5% for 9-17-year-old subjects. Inverse associations were demonstrated between: (i) %TLCCT with high attenuation and age (r2 = 0.49; p < 0.0001); (ii) %TLCCT with low attenuation and TLCCT (r2 = 0.47; p < 0.0001); (iii) %TLCCT with high attenuation and TLCCT (r2 = 0.76; p < 0.0001). In conclusion, quantitative analysis of chest CTs from children without lung disease can be used to define age-specific LAT and HAT for evaluation of pediatric lung disease severity.