Inspiratory and expiratory CT lung density in infants and young children.

BACKGROUND: There is a lack of information on normal inspiratory and expiratory CT lung density in infants. OBJECTIVE: To describe normal regional CT lung density at end inspiratory and end expiratory lung volumes in children ages 0--5 years. MATERIALS AND METHODS: Motionless HRCT images were obtained at 25 cm (inspiratory) and 0 cm (expiratory) water pressure at apical (top of arch) and basal (2 cm above diaphragm) levels in 16 sedated children (mean age 1.5 years) who underwent CT for reasons other than respiratory disease. Density was measured at anterior-posterior and medial-lateral locations at each level in each lung. The influence of level, location, and age was quantified using analysis of variance methods. RESULTS: Lung density declined linearly in the first few years of life and thereafter approximated adult values. Beginning with the anterior-basal location, density at end inspiration (HU)=-835-(16 x age in years)+16 (if apical)+33 (if posterior)+23 (if medial)+14 (if lateral); standard error=38. At resting end exhalation =-616-(41 x age)+50 (if apical)+155 (if posterior)+74 (if medial)+46 (if lateral); standard error=68. CONCLUSION: We provide an initial basis for employing lung densitometry in infants and young children at end inspiration and resting end exhalation lung volumes.