Estimation of total lung capacity from chest radiography and chest CT in children: comparison with body plethysmography.
OBJECTIVE: The purpose of this study was to evaluate two methods of estimating lung volume using chest radiographs and one using chest CT in children. Estimates made with these techniques were compared with total lung capacity calculated with body plethysmography. MATERIALS AND METHODS: CT scans and posteroanterior and lateral radiographs of the chest were obtained in 21 children (14 girls and seven boys) for follow-up evaluation after lung transplantation. Lung volume was measured by CT using a previously validated technique of tracing the margins of the lungs on each axial CT scan. Two methods were used to estimate lung volume on chest radiographs: a technique previously described in adults and children that requires 21 measurements on posteroanterior and lateral radiographs, and a modification of a simplified technique previously reported in adults that uses only two measurements on a posteroanterior radiograph alone. Estimated lung volumes from CT and from both methods using chest radiographs were compared with total lung capacity determined from body plethysmography using regression analysis, and 95% prediction intervals were generated. RESULTS: All three methods of estimating lung volumes from radiographs correlated well with total lung capacity from plethysmography (r = .89-.92). However, we found no statistically significant or clinically meaningful difference among the methods of estimating lung volume. CONCLUSIONS: Lung volumes in children can be accurately estimated from specific measurements made on chest radiographs and on CT scans. Of the two methods tested with chest radiographs, the technique that required only two measurements from a posteroanterior chest radiograph was as accurate as the more complicated technique that required 21 measurements.