ESTIMATION OF TOTAL LUNG CAPACITY FROM CHEST RADIOGRAPHY AND CHEST CTIN CHILDREN - COMPARISON WITH BODY PLETHYSMOGRAPHY

OBJECTIVE. The purpose of this study was to evaluate two methods of es timating lung volume using chest radiographs and one using chest CT in children. Estimates made with these techniques were compared with tot al lung capacity calculated with body plethysmography. MATERIALS AND M ETHODS. CT scans and posteroanterior and lateral radiographs of the ch est 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 th e lungs on each axial CT scan. Two methods were used to estimate lung volume on chest radiographs: a technique previously described in adult s and children that requires 21 measurements on posteroanterior and la teral radiographs, and a modification of a simplified technique previo usly reported in adults that uses only two measurements on a posteroan terior 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 9 5% prediction intervals were generated. RESULTS, All three methods of estimating lung Volumes from radiographs correlated well with total lu ng capacity from plethysmography (r=.89-.92). However, we found no sta tistically significant or clinically meaningful difference among the m ethods of estimating lung volume. CONCLUSIONS. Lung volumes in childre n can be accurately estimated from specific measurements made on chest radiographs and on CT scans. Of the two methods tested with chest rad iographs, the technique that required only two measurements from a pos teroanterior chest radiograph was as accurate as the more complicated technique that required 21 measurements.